Our award-winning ad campaign helps raise awareness of housing discrimination and calls on the public to report discrimination to HUD. The ads can be seen and heard on TV and radio nationwide. View the TV/Radio Ads.

Want advice on buying a home, renting, default, foreclosure, credit issues or reverse mortgages? HUD sponsors certain housing counseling agencies throughout the country who in turn give advice free or at low cost.

Making your home more energy efficient with ENERGY STAR can help to reduce high energy bills and improve comfort. Many common home problems like moisture on window panes; ice dams; peeling paint; and mold, can also often be solved by taking steps to improve energy efficiency.

Improving energy efficiency with ENERGY STAR is also an important first step in the growing trend of “green remodeling.” That’s because the energy we use in our homes often comes from the burning of fossil fuels at power plants, which contributes to smog, acid rain, and global warming. So, the less energy we use in our homes, the less air pollution we generate.

ENERGY STAR can guide you in making your home more energy efficient — whether you do-it-yourself or hire a qualified professional. Take these steps to get started or use the new ENERGY STAR Home Advisor to get specific, customized recommendations on how you can make your home more energy efficient, cut utility bills, and improve comfort — all while helping to protect the environment.

Analyze your Home’s Energy Use

If you have five minutes and your last 12 months of utility bills, use the ENERGY STAR Home Energy Yardstick to compare your home’s energy efficiency to similar homes across the country and get recommendations for energy-saving home improvements from ENERGY STAR. Or, hire a professional to perform a comprehensive home energy audit.

Air Seal and Insulate with ENERGY STAR Home Sealing

Sealing air leaks that cause uncomfortable drafts and adding insulation are two of the most cost-effective ways to improve the energy efficiency and comfort of your home. Use ENERGY STAR Home Sealing to guide you in making these improvements that every home should have.

Heat and Cool Efficiently

Learn to make smart decisions about heating and cooling efficiently. Change your air filter regularly, install a programmable thermostat, seal your heating and cooling ducts, and consider installing ENERGY STAR qualified heating and cooling equipment.

Veterans or servicemembers who have specific service-connected disabilities may be entitled to a grant from the Department of Veterans Affairs (VA) for the purpose of constructing an adapted home or modifying an existing home to meet their adaptive needs.  The goal of the Specially Adapted Housing (SAH) Grant Program is to provide a barrier-free living environment that affords the veterans or servicemembers a level of independent living he or she may not normally enjoy.

There are two types of grants administered by VA, which are available to assist severely disabled veterans or servicemembers in adapting housing to their special needs.

To avoid becoming a victim of fraud, work only with a HUD-approved Title 1 lender. This allows you to select the contractor and helps to prevent inflated estimates that only increase costs.

The top 10 home improvements reported were:

1. Levered doorknobs.



2. Grab bars in bathrooms.



3. Levered faucets in kitchen sinks.



4. Handrails on both sides of stairwells and on front and rear steps.



5. Grab bars in showers; removal of any door threshold.



6. Movable shower heads for those who must sit.



7. Portable shower seats.



8. A bathroom with a bath/shower as well as a bedroom on the first floor.



9. Widened doors to accommodate wheelchairs.



10. Ramps for those using walkers and wheelchairs.

The Single-Family Housing Program provides homeownership opportunities to low and moderate-income rural Americans through several loan, grant, and guarantee programs. The program also makes funding available to individuals to finance vital improvements necessary to make their homes decent, safe, and sanitary.

Direct Loan Program (Section 502)

Under the Direct Loan program, individuals or families receive direct financial assistance directly from the Housing and Community Facilities Programs in the form of a home loan at an affordable interest rate.

Most of the loans made under the Direct Loan Program are to families with income below 80% of the median income level in the communities where they live. Since HCFP is able to make loans to those who will not qualify for a conventional loan, the HCFP Direct Loan program enables many more people to buy homes than might otherwise be possible. Direct loans may be made for the purchase of an existing home or for new home construction.

Loan Guarantee Program (Section 502) 

Under the Guaranteed Loan program, the Housing and Community Facilities Programs guarantees loans made by private sector lenders. (A loan guarantee through HCFP means that, should the individual borrower default on the loan, HCFP will pay the private financier for the loan.) The individual works with the private lender and makes his or her payments to that lender.

Under the terms of the program, an individual or family may borrow up to 100% of the appraised value of the home, which eliminates the need for a down payment. Since a common barrier to owning a home for many low-income people is the lack of funds to make a down payment, the availability of the loan guarantees from HCFP makes the reality of owning a home available to a much larger percentage of Americans.

Mutual Self-Help Housing Program (Section 523)

The Mutual Self-Help Housing Program makes homes affordable by enabling future homeowners to work on homes themselves. With this investment in the home, or "sweat equity", each homeowner pays less for his or her home. Each qualified applicant is required to complete 65% of the work to build his or her own home.

Technical Assistance Grants and Site Loans are provided to nonprofit and local government organizations, which supervise groups of 5 to 12 enrollees in the Self-Help Program. Members of each group help work on each other's homes, moving in only when all the homes are completed.

Once accepted into the Self-Help Housing Program, each individual enrollee generally applies for a Single-Family Housing Direct Loan (Section 502).

Home Repair Loan and Grant Program (Section 504)

For very low income families who own homes in need of repair, the Home Repair Loan and Grant Program offers loans and grants for renovation. The Home Repair Program also provides funds to make a home accessible to someone with disabilities.

Money may be provided, for example, to repair a leaking roof; to replace a wood stove with central heating; to construct a front-door ramp for someone using a wheelchair; or to replace an outhouse and pump with running water, a bathroom, and a waste disposal system.

Being a community organizer is hard work - but it is so worthwhile! Whether you're just beginning or you've already graduated to nonprofit status, we have something for you.

If too little outdoor air enters a home, pollutants can sometimes accumulate to levels that can pose health and comfort problems. Likewise, one approach to lowering the concentrations of indoor air pollutants in your home is to increase the amount of outdoor air coming in.

Whether you’re planning an addition for a growing family or simply getting new storm windows, finding a competent and reliable contractor is the first step to a successful and satisfying home improvement project.

Your home may be your most valuable financial asset. That’s why it’s important to be cautious when you hire someone to work on it. Home improvement and repair and maintenance contractors often advertise in newspapers, the Yellow Pages, and on the radio and TV. However, don’t consider an ad an indication of the quality of a contractor’s work. Your best bet is a reality check from those in the know: friends, neighbors, or co-workers who have had improvement work done. Get written estimates from several firms. Ask for explanations for price variations. Don’t automatically choose the lowest bidder.

Recent News:
This Old House's Kevin O'Connor Helps ICI Paints Donate 100 Gallons of Paint To Historical Commission

ICI Paints, an international leader in the manufacture, marketing and distribution of world-class paint brands including Glidden and Ralph Lauren, today introduced the new line of This Old House exterior paint - now available exclusively in the Boston area - with the help of This Old House TV show host Kevin O'Connor. This Old House, widely regarded as a leading authority in home remodeling and restoration, entered a licensing agreement with ICI Paints in January to manufacture, distribute and market a new line of paint under the This Old House brand. This Old House paint will launch nationwide in early 2005. The Cambridge Historical Commission received a donation of 100 gallons of paint from the show. Susan Maycock, Survey Director, accepted the donation on behalf of the Commission and explained that the paint will be used as part of the Commission's Preservation Grants Program. This City program, established in 1976, helps low- and moderate-income families repair and restore original exterior features of their Cambridge homes, such as porches, ornamental trim, windows, clapboards, and shingles. Commission staff consult with grant recipients on historically-appropriate paint colors for their house style. The donated paint will be used for the exterior of the houses.

♣The Royal Coffee Bar is located in down town Phoenix and is close to a wide variety of entertainment for your leisure pleasure. Located just a block away from America West Arena it is the perfect place for a pick me up before a game or a concert or a warm up on a cold day. The atmosphere at The Royal Coffee Bar is a level above cool. On weekends there is D.J.'s spinning down beats and videos on the flat pannel. You can sit back and enjoy your coffee and pastry inside or out. There is plush seating for all to feel at home with a staff that is one of a kind. Patio seating is also avalliable with cover looking out into our thriving metropolis. Come in, kick back and get away.

The Icehouse, known historically as Constable Ice Storage, is located in the historically original town site of the city of Phoenix, Arizona. It began operations in 1910 as an ice house, manufacturing 300lb ice blocks for use in the food industry, primarily to keep produce cold as it was shipped by railroad to Eastern U.S. cities. Prior to its current arts use, the building was used by the police as storage for crime evidence. in 1990, Helen Hestenes and David Therrien began transforming The Icehouse into a center for the exhibition and exploration of new art forms, with emphasis on large scale works, installation, experimentation and community education.                                                                                                                             

 The Icehouse is now a venue for art shows and night life. Anything you can dream of The Icehouse has a place for it. Its dark Gothic like atmosphere gives the place an mysterious presence, a dungeon converted into a coffee house. It is a local hot spot, the movie “The Kingdom”, by Universal Pictures was shot on the site. It is 30,000 square feet of viewing pleasure with three public rooms which have housed exhibits from a wide variety of artists over the past 15 years. It also caters to corporate parties, weddings, music shows, raves and, most notably, local art exhibitions.
Known as an artist-run project, The Icehouse leases several rooms to local artists such as filmmakers and photographers. The Icehouse works hard to keep up the atmosphere local and grounded. Local artists create installation art specifically created for the occasion and often destroy it afterwards.

The focus of The Icehouse is to showcase large scale works that are usually not commercial and not for sale, but are more on ideas that are very powerful. The profits from the leasing are donated for various art projects, including First Friday Art walk and CRASHarts, a non profit art organization.

The Icehouses history is a lavish one. It had a big impact in the 90's and is still setting grounds for todays art world making it an oasis of happiness. The place is based so much on heart and soul, it has a magical human element about it that people know and love. It is not just a gallery with a painting on the wall for 25,000 dollars, it is something more, it is a strong survivor. The Icehouse will continue to be a buried treasure and an invisible secret as well as downtown Phoenixes landmark of endless possibilities.

What can you do?

About Poison

• Read warning labels and follow storage directions on household products.
• Poisonous products can include medicines, cleaning supplies, hair spray, and home repair materials.
• Keep poisonous products out of children’s sight and reach on high shelves. Install child-proof latches on cabinets that do not have locks.
• Store food and non-food products separately to prevent confusion and protect your family from container contamination and toxic spills.
• Always choose non-toxic alternatives when possible and use products with child-resistant caps.
• Never mix cleaning products together; they may produce dangerous fumes (ammonia and bleach should never be mixed).
• Install Carbon Monoxide (CO) detectors in your home.
• Flush expired medicines down the toilet rather than throwing them in the garbage.
• If it is necessary to use harsh chemicals, use them when children are not at home, or at least are in a different room. Always wear gloves when handling products that could be toxic and follow all manufacturers’ instructions.

About Fires and Burns

• Install smoke detectors on every floor of your home near every bedroom. Test detectors every month and change their batteries every year. Never disable smoke detectors.
• Develop a family escape plan.
• Keep matches, lighters, and candles out of children’s reach. Never smoke in bed. It is the leading cause of fire-related deaths.
• Keep anything that can catch fire away from fireplaces, heaters, and radiators. Replace frayed electrical wires.
• Take care to avoid kitchen fires and burns. - Stay in the kitchen while cooking. - Turn pot handles toward the inside of the stove so children cannot grab them. - Install ground-fault circuit interrupters (GFCIs) in kitchens and bathrooms.
• Set water-heater thermostats below 120° F (50° C). Always test the water before bathing yourself or your child.

About Drowning, Choking, Suffocation, and Strangulation

• Never leave children alone near water, including bathtubs, buckets, swimming pools, rivers, and the ocean. Learn and practice First Aid and CPR.
• Use child-proof fencing around all swimming pools and hot-tubs.
• Avoid toys for children under 3 years of age that are smaller than 2 inches long and 1 inche wide. Toys for young children should never have small or removable parts that could be choked on.
• Avoid window blinds with looped cords, which may cause strangulation if not stored out of children’s reach.Keep plastic bags and drawstring cords away from children.

About Falls and Other Injuries

• Keep your floors free of anything that may cause tripping, such as toys, shoes, or magazines.
• Use stools, ladders and stepladders carefully.
• Make sure that your home is well lit.Use guards on windows and safety gates near stairs to keep children from falling
• Follow manufacturers’ instructions for storing and using lawn equipment or chemicals.
• Wear protective gear on eyes and ears when using power tools.
• Keep sharp or electronic kitchen and bathroom items out of children’s reach. Keep electric appliances away from water.
• Always keep firearms well secured. Firearms should always be locked, unloaded, and stored out of reach. Store ammunition in a separate, locked location.

• Do not allow film and scale to develop in your humidifier. If possible, change the water in your room humidifier daily. Empty the tank before you fill it. If the tank is not removable, clean it often according to manufacturer's instructions.
  
  
• Use distilled or demineralized water in your room humidifier to reduce the buildup of scale and the release of dust. Do not use tap water because it contains more minerals. Use demineralization cartridges or filters if supplied or recommended for use with your humidifier.
  
  
• Drain and clean the tank of your room humidifier before you store it. Clean it after summer storage. Remove dust on the outside of your unit.
  
  
• Clean your room humidifier well and often during the heating season. Be sure to unplug the humidifier before cleaning. Follow the manufacturer's suggested cleaning methods. If chlorine bleach or other cleaning product or disinfectant is used, make sure to rinse the tank well to avoid breathing harmful chemicals. Use a brush or other scrubber to clean the tank. Be careful not to damage the motor or to scratch the inner surface. Clean or replace sponge filters or belts when needed.
  
  
• Maintain the relative humidity in your home between 30% and 50% if possible. Humidity levels above 60% may allow moisture to build up indoors and condense on surfaces, where bacteria and fungi can settle and grow. You can measure humidity with an instrument called a hygrometer, available at your local hardware store.
  

• Do not use portable heaters or lanterns while sleeping in enclosed areas such as tents, campers, and other vehicles. This is especially important at high altitudes, where the risk of carbon monoxide poisoning is increased.
  
  
• Know the symptoms of carbon monoxide poisoning: headache, dizziness, weakness, nausea, vomiting, sleepiness, and confusion. Carbon monoxide reduces the blood's ability to carry oxygen. Low blood oxygen levels can result in loss of consciousness and death.
  
  
• See a doctor if you or a member of your family develops cold or flu-like symptoms while camping. Carbon monoxide poisoning, which can easily be mistaken for a cold or flu, is often detected too late.
  
  
• Alcohol consumption and drug use increase the effects of carbon monoxide poisoning.
  
  
• Carbon monoxide is especially toxic to mother and child during pregnancy, infants, the elderly, smokers, and people with blood or circulatory system problems, such as anemia, or heart disease.
  
  
• CPSC is working with the camping equipment industry to limit the amount of carbon monoxide produced by portable heaters, lanterns, and stoves. Labels warning campers about carbon monoxide poisoning are being developed for these products.
  

Hazards may be associated with almost all types of appliances. The purpose of this booklet is to answer some common questions you may have about the potential for one specific type of hazard - indoor air pollution - associated with one class of appliances - combustion appliances.

Combustion appliances are those which burn fuels for warmth, cooking, or decorative purposes. Typical fuels are gas, both natural and liquefied petroleum (LP); kerosene; oil; coal; and wood. Examples of the appliances are space heaters, ranges, ovens, stoves, furnaces, fireplaces, water heaters, and clothes dryers. These appliances are usually safe. However, under certain conditions, these appliances can produce combustion pollutants that can damage your health, or even kill you.

POSSIBLE HEALTH EFFECTS range from headaches, dizziness, sleepiness, and watery eyes to breathing difficulties or even death. Similar effects may also occur because of common medical problems or other indoor air pollutants.

This booklet was written:

1. to encourage the proper use, maintenance, and installation of combustion appliances;
2. to discuss the pollutants produced by these appliances;
3. to describe how these pollutants can affect your health; and,
4. to tell you how you can reduce your exposure to them.

Should I be concerned about indoor air pollution?

YES. Studies have shown that the air in our homes can be even more polluted than the outdoor air in big cities. Because people spend a lot of time indoors, the quality of the air indoors can affect their health. Infants, young children and the elderly are a group shown to be more susceptible to pollutants. People with chronic respiratory or cardiovascular illness or immune system diseases are also more susceptible than others to pollutants.

Many factors determine whether pollutants in your home will affect your health. They include the presence, use, and condition of pollutant sources, the level of pollutants both indoors and out, the amount of ventilation in your home, and your overall health.

Most homes have more than one source of indoor air pollution. For example, pollutants come from tobacco smoke, building materials, decorating products, home furnishings, and activities such as cooking, heating, cooling, and cleaning. Living in areas with high outdoor levels of pollutants usually results in high indoor levels. Combustion pollutants are one category of indoor air pollutants.

What are combustion pollutants?

Combustion pollutants are gases or particles that come from burning materials. The combustion pollutants discussed in this booklet come from burning fuels in appliances. The common fuels burned in these appliances are natural or LP gas, fuel oil, kerosene, wood, or coal. The types and amounts of pollutants produced depend upon the type of appliance, how well the appliance is installed, maintained, and vented, and the kind of fuel it uses. Some of the common pollutants produced from burning these fuels are carbon monoxide, nitrogen dioxide, particles, and sulfur dioxide. Particles can have hazardous chemicals attached to them. Other pollutants that can be produced by some appliances are unburned hydrocarbons and aldehydes.

Combustion always produces water vapor. Water vapor is not usually considered a pollutant, but it can act as one. It can result in high humidity and wet surfaces. These conditions encourage the growth of biological pollutants such as house dust mites, molds, and bacteria.

Where do combustion pollutants come from?

Combustion pollutants found indoors include: outdoor air, tobacco smoke, exhaust from car and lawn mower internal combustion engines, and some hobby activities such as welding, woodburning, and soldering. Combustion pollutants can also come from vented or unvented combustion appliances. These appliances include space heaters, gas ranges and ovens, furnaces, gas water heaters, gas clothes dryers, wood or coal-burning stoves, and fireplaces. As a group these are called "combustion appliances."

What is a vented appliance?
What is an unvented appliance?

Vented appliances are appliances designed to be used with a duct, chimney, pipe, or other device that carry the combustion pollutants outside the home. These appliances can release large amounts of pollutants directly into your home, if a vent is not properly installed, or is blocked or leaking.

Unvented appliances do not vent to the outside, so they release combustion pollutants directly into the home.

Look at the box below for typical appliance problems that cause the release of pollutants in your home. Many of these problems are hard for a homeowner to identify. A professional is needed.

COMBUSTION APPLIANCES AND POTENTIAL PROBLEMS

Can I use charcoal grills or charcoal hibachis indoors?

No. Never use these appliances inside homes, trailers, truck-caps, or tents. Carbon monoxide from burning and smoldering charcoal can kill you if you use it indoors for cooking or heating. There are about 25 deaths each year from the use of charcoal grills and hibachis indoors.

NEVER burn charcoal inside homes, trailers, tents, or other enclosures. The carbon monoxide can kill you.

What are the health effects of combustion pollutants?

The health effects of combustion pollutants range from headaches and breathing difficulties to death. The health effects may show up immediately after exposure or occur after being exposed to the pollutants for a long time. The effects depend upon the type and amount of pollutants and the length of time of exposure to them. They also depend upon several factors related to the exposed person. These include the age and any existing health problems. There are still some questions about the level of pollutants or the period of exposure needed to produce specific health effects. Further studies to better define the release of pollutants from combustion appliances and their health effects are needed.

The sections below discuss health problems associated with some common combustion pollutants. These pollutants include carbon monoxide, nitrogen dioxide, particles, and sulfur dioxide. Even if you are healthy, high levels of carbon monoxide can kill you within a short time. The health effects of the other pollutants are generally more subtle and are more likely to affect susceptible people. It is always a good idea to reduce exposure to combustion pollutants by using and maintaining combustion appliances properly.

Carbon Monoxide:

Each year, according to CPSC, there are more than 200 carbon monoxide deaths related to the use of all types of combustion appliances in the home. Exposure to carbon monoxide reduces the blood's ability to carry oxygen. Often a person or an entire family may not recognize that carbon monoxide is poisoning them. The chemical is odorless and some of the symptoms are similar to common illnesses. This is particularly dangerous because carbon monoxide's deadly effects will not be recognized until it is too late to take action against them.

Carbon monoxide exposures especially affect unborn babies, infants, and people with anemia or a history of heart disease. Breathing low levels of the chemical can cause fatigue and increase chest pain in people with chronic heart disease. Breathing higher levels of carbon monoxide causes symptoms such as headaches, dizziness, and weakness in healthy people. Carbon monoxide also causes sleepiness, nausea, vomiting, confusion, and disorientation. At very high levels it causes loss of consciousness and death.

Nitrogen Dioxide:

Breathing high levels of nitrogen dioxide causes irritation of the respiratory tract and causes shortness of breath. Compared to healthy people, children, and individuals with respiratory illnesses such as asthma, may be more susceptible to the effects of nitrogen dioxide.

Some studies have shown that children may have more colds and flu when exposed to low levels of nitrogen dioxide. When people with asthma inhale low levels of nitrogen dioxide while exercising, their lung airways can narrow and react more to inhaled materials.

Particles:

Particles suspended in the air can cause eye, nose, throat, and lung irritation. They can increase respiratory symptoms, especially in people with chronic lung disease or heart problems. Certain chemicals attached to particles may cause lung cancer, if they are inhaled. The risk of lung cancer increases with the amount and length of exposure. The health effects from inhaling particles depend upon many factors, including the size of the particle and its chemical make-up.

Sulfur Dioxide:

Sulfur dioxide at low levels of exposure can cause eye, nose, and respiratory tract irritation. At high exposure levels, it causes the lung airways to narrow. This causes wheezing, chest tightness, or breathing problems. People with asthma are particularly susceptible to the effects of sulfur dioxide. They may have symptoms at levels that are much lower than the rest of the population.

Other Pollutants:

Combustion may release other pollutants. They include unburned hydrocarbons and aldehydes. Little is known about the levels of these pollutants in indoor air and the resulting health effects.

What do I do if I suspect that combustion pollutants are affecting my health?

If you suspect you are being subjected to carbon monoxide poisoning get fresh air immediately. Open windows and doors for more ventilation, turn off any combustion appliances, and leave the house. You could lose consciousness and die from carbon monoxide poisoning if you do nothing. It is also important to contact a doctor IMMEDIATELY for a proper diagnosis. Remember to tell your doctor that you suspect carbon monoxide poisoning is causing your problems. Prompt medical attention is important.

Remember that some symptoms from combustion pollutants - headaches, dizziness, sleepiness, coughing, and watery eyes - may also occur because of common medical problems. These medical problems include colds, the flu, or allergies. Similar symptoms may also occur because of other indoor air pollutants. Contact your doctor for a proper diagnosis.

To help your doctor make the correct diagnosis, try to have answers to the following questions:

• Do your symptoms occur only in the home? Do they disappear or decrease when you leave home, and reappear when you return?
• Is anyone else in your household complaining of similar symptoms, such as headaches, dizziness, or sleepiness? Are they complaining of nausea, watery eyes, coughing, or nose and throat irritation?
• Do you always have symptoms?
• Are your symptoms getting worse?
• Do you often catch colds or get the flu?
• Are you using any combustion appliances in your home?
• Has anyone inspected your appliances lately? Are you certain they are working properly?
  

Your doctor may take a blood sample to measure the level of carbon monoxide in your blood if he or she suspects carbon monoxide poisoning. This sample will help determine whether carbon monoxide is affecting your health.

Contact qualified appliance service people to have your appliances inspected and adjusted if needed. You should be able to find a qualified person by asking your appliance distributor or your fuel supplier. In some areas, the local fuel company may be able to inspect and adjust the appliance.

How can I reduce my exposure to combustion pollutants?

Proper selection, installation, inspection and maintenance of your appliances are extremely important in reducing your exposure to these pollutants. Providing good ventilation in your home and correctly using your appliance can also reduce your exposure to these pollutants.

Additionally, there are several different residential carbon monoxide detectors for sale. The CPSC is encouraging the development of detectors that will provide maximum protection. These detectors would warn consumers of harmful carbon monoxide levels in the home. They may soon be widely available to reduce deaths from carbon monoxide poisoning.

APPLIANCE SELECTION

• Choose vented appliances whenever possible.
• Only buy combustion appliances that have been tested and certified to meet current safety standards. Examples of certifying organizations are Underwriters Laboratories (UL) and the American Gas Association (AGA) Laboratories. Look for a label that clearly shows the certification.
• All currently manufactured vented gas heaters are required by industry safety standards to have a safety shut-off device. This device helps protect you from carbon monoxide poisoning by shutting off an improperly vented heater.
• Check your local and state building codes and fire ordinances to see if you can use an unvented space heater, if you consider purchasing one. They are not allowed to be used in some communities, dwellings, or certain rooms in the house.
• If you must replace an unvented gas space heater with another, make it a new one. Heaters made after 1982 have a pilot light safety system called an oxygen depletion sensor (ODS). This system shuts off the heater when there is not enough fresh air, before the heater begins producing large amounts of carbon monoxide. Look for the label that tells you that the appliance has this safety system. Older heaters will not have this protection system.
• Consider buying gas appliances that have electronic ignitions rather than pilot lights. These appliances are usually more energy efficient and eliminate the continuous low-level pollutants from pilot lights.
• Buy appliances that are the correct size for the area you want to heat. Using the wrong size heater may produce more pollutants in your home and is not an efficient use of energy.
• Talk to your dealer to determine the type and size of appliance you will need. You may wish to write to the appliance manufacturer or association for more information on the appliance. Some addresses are in the back of this booklet.
• All new woodstoves are EPA-certified to limit the amounts of pollutants released into the outdoor air. For more information on selecting, installing, operating, and maintaining woodburning stoves, write to the EPA Wood Heater Program. Their address is at the bottom of this booklet. Before buying a woodstove check your local laws about the installation and use of woodstoves.
  

Proper Installation

You should have your appliances professionally installed. Professionals should follow the installation directions and applicable building codes. Improperly installed appliances can release dangerous pollutants in your home and may create a fire hazard. Be sure that the installer checks for backdrafting on all vented appliances. A qualified installer knows how to do this.

Ventilation

• To reduce indoor air pollution, a good supply of fresh outdoor air is needed. The movement of air into and out of your home is very important. Normally, air comes through cracks around doors and windows. This air helps reduce the level of pollutants indoors. This supply of fresh air is also important to help carry pollutants up the chimney, stovepipe, or flue to the outside.
• Keep doors open to the rest of the house from the room where you are using an unvented gas space heater or kerosene heater, and crack open a window. This allows enough air for proper combustion and reduces the level of pollutants, especially carbon monoxide.
• Use a hood fan, if you are using a range. They reduce the level of pollutants you breath, if they exhaust to the outside. Make sure that enough air is coming into the house when you use an exhaust fan. If needed, slightly open a door or window, especially if other appliances are in use. For proper operation of most combustion appliances and their venting system, the air pressure in the house should be greater than that outside. If not, the vented appliances could release combustion pollutants into the house rather than outdoors. If you suspect that you have this problem you may need the help of a qualified person to solve it.
• Make sure that your vented appliance has the vent connected and that nothing is blocking it. Make sure there are no holes or cracks in the vent. Do not vent gas clothes dryers or water heaters into the house for heating. This is unsafe.
• Open the stove's damper when adding wood. This allows more air into the stove. More air helps the wood burn properly and prevents pollutants from being drawn back into the house instead of going up the chimney. Visible smoke or a constant smoky odor inside the home when using a woodburning stove is a sign that the stove is not working properly. Soot on furniture in the rooms where you are using the stove also tells this. Smoke and soot are signs that the stove is releasing pollutants into the indoor air.
  

Correct Use

• Read and follow the instructions for all appliances so you understand how they work. Keep the owner's manual in a convenient place to refer to when needed. Also, read and follow the warning labels because they tell you important safety information that you need to know. Reading and following the instructions and warning labels could save your life.
• Always use the correct fuel for the appliance.
• Only use water-clear ASTM 1-K kerosene for kerosene heaters. The use of kerosene other than 1-K could lead to a release of more pollutants in your home. Never use gasoline in a kerosene heater because it can cause a fire or an explosion. Using even small amounts of gasoline could cause a fire.
• Use seasoned hardwoods (elm, maple, oak) instead of softwoods (cedar, fir, pine) in woodburning stoves and fireplaces. Hardwoods are better because they burn hotter and form less creosote, an oily, black tar that sticks to chimneys and stove pipes. Do not use green or wet woods as the primary wood because they make more creosote and smoke. Never burn painted scrap wood or wood treated with preservatives, because they could release highly toxic pollutants, such as arsenic or lead. Plastics, charcoal, and colored paper such as comics, also produce pollutants. Never burn anything that the stove or fireplace manufacturer does not recommend.
• Never use a range, oven, or dryer to heat your home. When you misuse gas appliances in this way, they can produce fatal amounts of carbon monoxide. They can produce high levels of nitrogen dioxide, too.
• Never use an unvented combustion heater overnight or in a room where you are sleeping. Carbon monoxide from combustion heaters can reach dangerous levels.
• Never ignore a safety device when it shuts off an appliance. It means that something is wrong. Read your appliance instructions to find out what you should do or have a professional check out the problem.
• Never ignore the smell of fuel. This usually indicates that the appliance is not operating properly or is leaking fuel. Leaking fuel will not always be defectible by smell. If you suspect that you have a fuel leak have it fixed as soon as possible. In most cases you should shut off the appliance, extinguish any other flames or pilot lights, shut off other appliances in the area, open windows and doors, call for help, and leave the area.
  

Inspection and Maintenance

• Have your combustion appliance regularly inspected and maintained to reduce your exposure to pollutants. Appliances that are not working properly can release harmful and even fatal amounts of pollutants, especially carbon monoxide.
• Have chimneys and vents inspected when installing or changing vented heating appliances. Some modifications may be required. For example, if a change was made in your heating system from oil to natural gas, the flue gas produced by the gas system could be hot enough to melt accumulated oil combustion debris in the chimney or vent. This debris could block the vent forcing pollutants into the house. It is important to clean your chimney and vents especially when changing heating systems.

What are the inspection and maintenance procedures?

In general, check the flame in the furnace combustion chamber at the beginning of the heating season. Natural gas furnaces should have a blue flame with perhaps only a slight yellow tip. Call your appliance service representative to adjust the burner if there is a lot of yellow in the flame, or call your local utility company for this service. LP units should have a flame with a bright blue center that may have a light yellow tip. Pilot lights on gas water heaters and gas cooking appliances should also have a blue flame. Have a trained service representative adjust the pilot light if it is yellow or orange.

Before each heating season, have flues and chimneys inspected and cleaned before each heating season for leakage and for blockage by creosote or debris. Creosote buildup or leakage could cause black stains on the outside of the chimney or flue. These stains can mean that pollutants are leaking into the house.

The chart below shows how and when to take care of your appliance.

This booklet discussed the types of pollutants that may be produced by combustion appliances, described how they might affect your health, and suggested ways you could reduce your exposure to them. It also explained that proper appliance selection, installation, operation, inspection, and maintenance are very important in reducing exposure to combustion pollutants.

INSPECTION AND MAINTENANCE SCHEDULES

What Are Biological Pollutants?

• Animal Dander (minute scales from hair, feathers, or skin)
  
• Dust Mite and Cockroach parts
  
  
• Infectious agents (bacteria or viruses)
  
• Pollen
  
  

The Scope Of The Problem

Health Effects Of Biological Pollutants

• Allergic
  
• Infectious
  
• Toxic
  

• Watery eyes
  
• Runny nose and sneezing
  
• Nasal congestion
  
• Itching
  
• Coughing
  
• Wheezing and difficulty breathing
  
• Headache
  
• Fatigue
  

Talking to Your Doctor

• Does anyone in the family have frequent headaches, fevers, itchy watery eyes, a stuffy nose, dry throat, or a cough? Does anyone complain of feeling tired or dizzy all the time? Is anyone wheezing or having difficulties breathing on a regular basis?
  
• Did these symptoms appear after you moved to a new or different home?
  
• Do the symptoms disappear when you go to school or the office or go away on a trip, and return when you come back?
  
• Have you recently remodeled your home or done any energy conservation work, such as installing insulation, storm windows, or weather stripping? Did your symptoms occur during or after these activities?
  
• Does your home feel humid? Can you see moisture on the windows or on other surfaces, such as walls and ceilings?
  
• What is the usual temperature in your home? Is it very hot or cold?
  
• Have you recently had water damage?
  
• Is your basement wet or damp?
  
• Is there any obvious mold or mildew?
  
• Does any part of your home have a musty or moldy odor?
  
• Is the air stale?
  
• Do you have pets?
  
• Do your house plants show signs of mold?
  
• Do you have air conditioners or humidifiers that have not been properly cleaned?
  
• Does your home have cockroaches or rodents?
  

Coping With the Problem

• Dust and construction materials, such as wood, wallboard, and insulation, contain nutrients that allow biological pollutants to grow. Firewood also is a source of moisture, fungi, and bugs.
  
• Appliances such as humidifiers, kerosene and gas heaters, and gas stoves add moisture to the air.
• A musty odor, moisture on hard surfaces, or even water stains, may be caused by:

Air-conditioning units
Basements, attics, and crawlspaces
Bathrooms
Carpets
Heating and air-conditioning ducts
Humidifiers and dehumidifiers
Refrigerator drip pans

What You Can Do About Biological Pollutants

• Fix leaks and seepage. If water is entering the house from the outside, your options range from simple landscaping to extensive excavation and waterproofing. (The ground should slope away from the house). Water in the basement can result from the lack of gutters or a water flow toward the house. Water leaks in pipes or around tubs and sinks can provide a place for biological pollutants to grow.
  
• Put a plastic cover over dirt crawlspaces to prevent moisture from coming in from the ground. Be sure crawlspaces are well-ventilated.
  
• Use exhaust fans in bathrooms and kitchens to remove moisture to the outside (not into the attic) Vent your clothes dryer to the outside.
  
• Turn off certain appliances (such as humidifiers or kerosene heaters) if you notice moisture on windows and other surfaces.
  
• Use dehumidifiers and air conditioners, especially in hot, humid climates, to reduce moisture in the air, but be sure that the appliances themselves don't become sources of biological pollutants.
  
• Raise the temperature of cold surfaces where moisture condenses. Use insulation or storm windows. (A storm window installed on the inside works better than one installed on the outside ) Open doors between rooms (especially doors to closets which may be colder than the rooms) to increase circulation. Circulation carries heat to the cold surfaces Increase air circulation by using fans and by moving furniture from wall corners to promote air and heat circulation. Be sure that your house has a source of fresh air and can expel excessive moisture from the home.
  
• Pay special attention to carpet on concrete floors. Carpet can absorb moisture and serve as a place for biological pollutants to grow. Use area rugs which can be taken up and washed often In certain climates, if carpet is to be installed over a concrete floor, it maybe necessary to use a vapor barrier (plastic sheeting) over the concrete and cover that with sub-flooring (insulation covered with plywood) to prevent a moisture problem.
  
• Moisture problems and their solutions differ from one climate to another. The Northeast is cold and wet, the Southwest is hot and dry, the South is hot and wet, and the Western Mountain states are cold and dry. All of these regions can have moisture problems. For example, evaporative coolers used in the Southwest can encourage the growth of biological pollutants. In other hot regions, the use of air conditioners which cool the air too quickly may prevent the air conditioners from running long enough to remove excess moisture from the air. The types of construction and weatherization for the different climates can lead to different problems and solutions.

Where Biological Pollutants May Be Found in the Home

1. Dirty air conditioners 2. Dirty humidifiers and/or dehumidifiers 3. Bathroom without vents or windows 4. Kitchen without vents or windows 5. Dirty refrigerator drip pans 6. Laundry room with unvented dryer 7. Unventilated attic

8. Carpet on damp basement floor 9. Bedding 10. Closet on outside wall 11. Dirty heating/air conditioning system 12. Dogs or cats 13. Water damage (around windows, the roof or the basement)

• Have major appliances, such as furnaces, heat pumps and central air conditioners, inspected and cleaned regularly by a professional, especially before seasonal use. Change filters on heating and cooling systems according to manufacturer's directions. (In general, change filters monthly during use.) When first turning on the heating or air conditioning at the start of the season, consider leaving your home until it airs out.
  
  
• Have window or wall air-conditioning units cleaned and serviced regularly by a professional, especially before the cooling season. Air conditioners can help reduce the entry of allergy-causing pollen. But they may also become a source of biological pollutants if not properly maintained. Clean the coils and rinse the drain pans according to manufacturer's instructions, so water can-not collect in pools.
  
  
• Have furnace-attached humidifiers cleaned and serviced regularly by a professional, especially before the heating season.
  
  
• Follow manufacturer's instructions when using any type of humidifier Experts differ on the benefits of using humidifiers. If you do use a portable humidifier (approximately 1 to 2 gallon tanks), be sure to empty its tank every day and refill with distilled or demineralized water, or even fresh tap water if the other types of water are unavailable For larger portable humidifiers, change the water as recommended by the manufacturer. Unplug the appliance before cleaning. Every third day, clean all surfaces coming in contact with water with a 3% solution of hydrogen peroxide, using a brush to loosen deposits Some manufacturers recommend using diluted household bleach for cleaning and maintenance, generally in a solution of one-half cup bleach to one gallon water When any household chemical, rinse well to remove all traces of chemical before refilling humidifier.
  
  
• Empty dehumidifiers daily and clean often. If possible, have the appliance drip directly into a drain. Follow manufacturer's instructions for cleaning and maintenance. Always disconnect the appliance before cleaning.
  
  
• Clean refrigerator drip pans regularly according to manufacturer's instructions. If refrigerator and freezer doors don't seal properly, moisture may build up and mold can grow. Remove any mold on door gaskets and replace faulty gaskets.
  
  

• Clean moist surfaces, such as showers and kitchen counters.
  
  
• Remove mold from walls, ceilings, floors, and paneling. Do not simply cover mold with paint, stain, varnish, or a moisture-proof sealer, as it may resurface.
  
  
• Replace moldy shower curtains, or remove them and scrub well with a household cleaner and rinse before rehanging them.
  
  

• Always wash bedding in hot water (at least 130° F) to kill dust mites. Cold water won't do the job. Launder bedding at least every 7 to 10 days.
  
  
• Use synthetic or foam rubber mattress pads and pillows, and plastic mattress covers if you are allergic Do not use fuzzy wool blankets, feather or wool-stuffed comforters, and feather pillows.
  
  
• Clean rooms and closets well, dust and vacuum often to remove surface dust. Vacuuming and other cleaning may not remove all animal dander, dust mite material, and other biological pollutants. Some particles are so small they can pass through vacuum bags and remain in the air If you are allergic to dust, wear a mask when vacuuming or dusting. People who are highly allergy-prone should not perform these tasks. They may even need to leave the house when someone else is cleaning.
  
  

Before You Move

• Have professionals check the heating and cooling system, including humidifiers and vents Have duct lining and insulation checked for growth.
  
• Check for exhaust fans in bathrooms and kitchens If there are no vents, do the kitchen and bathrooms have at least one window a piece? Does the cook top have a hood vented outside? Does the clothes dryer vent outside? Are all vents to the outside of the building, not in attics or crawlspaces?
• Look for obvious mold growth throughout the house, including attics, basements, and crawlspaces and around the foundation. See if there are many plants close to the house, particularly if they are damp and rotting. They are a potential source of biological pollutants. Downspouts from roof gutters should route water away from the building.
  
• Look for stains on the walls, floor or carpet (including any carpet over concrete floors) as evidence of previous flooding or moisture problems. Is there moisture on windows and surfaces? Are there signs of leaks or seepage in the basement?
  
• Look for rotted building materials which may suggest moisture or water damage.
  
• If you or anyone else in the family has a pet allergy, ask if any pets have lived in the home.
  
• Examine the design of the building. Remember that in cold climates, overhanging areas, rooms over unheated garages, and closets on outside walls may be prone to problems with biological pollutants.
  
• Look for signs of cockroaches.
  

Warning!

• Do not mix any chemical products. Especially, never mix cleaners containing bleach with any product (such as ammonia) which does not have instructions for such mixing When chemicals are combined, a dangerous gas can sometimes be formed.
  
  
• Household chemicals may cause burning or irritation to skin and eyes.
  
  
• Household chemicals may be harmful if swallowed, or inhaled.
  
  
• Avoid contact with skin, eyes, mucous membranes and clothing.
  
  
• Avoid breathing vapor. Open all windows and doors and use an exhaust fan that sends the air outside.
  
  
• Keep household chemicals out of reach of children.
  
  
• Rinse treated surface areas well to remove all traces of chemicals.
  
  

Correcting Water Damage

What if damage is already done? Follow these guidelines for correcting water damage:

GMR heads are currently one of the most static sensitive devices that are manufactured today. If they experience a voltage across them of 5-10 V they will draw enough current to destroy them in about 10 nsec. The situation is exacerbated by the fact that it takes very little handling to tribocharge a HSA or an HGA assembly to thousands of volts. Then, any contact with ground of the flex lines or head wiring will destroy a head and result in yield loss.

A complete electrostatic management program can make a dramatic improvement in yield losses due to electrostatic discharge (ESD). This includes a comprehensive program to ground all conductors, elimination of insulators wherever possible, specification of dissipative materials (and grounding them), and finally, the use of air ionization to bleed surface charge off of insulators and ungrounded conductors. The details of fixtures, gloves and of hand tools such as tweezers are critical elements in the electrostatic management program.

The action of air ionizers is to add very nearly equal numbers of positive and negative ions to the air in order to provide charge carriers that increase the electrical conductivity of the air. If only a small percent of the air molecules are ionized (~one millionth to 100 millionth %), the time for static discharge is reduced from hours to seconds.

Air ionizers are widely used by the disk drive manufacturing industry today. Most use either corona discharge or natural radiation (alpha) techniques to generate air ions. Both are commonly used today and each have certain advantages. Each are discussed below.

The Corona Method

This technique involves the use of high voltage (~5-20 kV) . The voltage is applied to a set of sharp points, an intense electric field is established in the very near (~100 mm.) of the points. This field accelerates free electrons to a sufficiently high energy to allow them to ionize molecules that they collide with. When the voltage on the point is positive, positive ions are repelled into the environment and when the point is negative, negative ions are delivered. Corona ionizers are made with AC voltage and with DC voltage. Each has certain benefits that are discussed below.

AC Ionizers

The AC ionizer is by far the simplest and therefore the lowest cost to manufacture. It utilizes a step-up transformer to create the high voltage for ion generation. See Figure 1.

Figure 1. Schematic diagram of an AC-type ionizer.

Because the transformer secondary is well isolated from ground, the current drawn from the emitter point(s) during the positive and negative voltage excursions of the emitter (corresponding to positive and negative excursions of the AC power line should be equal. Experience shows that the actual offset voltageas measured with a Charge Plate Monitor (CPM) is typically less than 5 V so indeed, the AC ionizer is self regulating.

Because the AC type ionizer produces the positive and negative ions in sequence from the same emitter point(s), these ions are separated in time by half of the period of the AC power line (i.e. 1/100 or 1/120 sec.). This means that the waves of positive and negative ions are rather close to each other, making loss through recombination a large factor. AC ionizers typically utilize fast airflow velocity to minimize recombination. This is not always desirable in a cleanroom environment.

DC Ionizers

DC Ionizers use separate emitter points for the positive and negative DC HV power supplies to create the ions. The voltage is applied to separate negative and positive emitter points. In order to provide equal numbers of positive and negative ions from separate sources, DC ionizers need some form of control to maintain this balance. For the demanding requirements of electrostatic management of production lines where GMR heads are handled, the control must be active feedback to account for variations in the environment and for any wear that occurs over the life of the ionizer. A schematic diagram of a DC type ionizer is shown in figure 2. Because of the greater sophistication and control systems that are needed for DC ionizers, the DC ionizing systems are more expensive to manufacture. Owing to the fact that the positive and negative emitters are well separated from each other, recombination is a lesser effect and the DC ionizer can sometimes utilize lower airflow velocity to deliver the ions to the location where the ionization is required.

Figure 2. Schematic of a DC-type ionizer.

The Alpha Ionizer Method

The use of ionizing radiation to make ions is the third technique that is employed for electrostatic management. While several forms of ionizing radiation sources are available, only a sources are used for static control..The other forms of source have much longer range and thus require shielding in impractical amounts Most commonly, Po²¹⁰ is employed because of its properties as an a emitter. It produces a particles with a range of only 3.8 cm. in air and 0.02 mm in aluminum so that virtually none of the a particles are emitted from the ionizing blower used at a workstation either through the air or through the chassis of the alpha source even if he handles the ionizer case extensively. Thus, alpha sources of this sort are regarded as harmless by government organizations in virtually every country. The other aspect of Po²¹⁰ that makes it an ideal choice is that it decays to Pb²⁰⁶ which is a naturally occurring stable isotope. Unlike Po²¹⁰, many other sources decay into isotopes that may be active as well.

The reason that the range of a particles is so short is that they move much slower than any other natural type of source and thus couple their energy much more efficiently to the air molecules, resulting in ionization. This makes an alpha type ionizer particularly efficient at creating ions and thus it provides fast discharge times.

The greatest advantage of an alpha ionizer is that is does not employ high voltage to create the ions and thus it does not emit electric fields, either AC or DC. Thus, a ionizers should have a balance voltage of zero, an important attribute as heads become smaller and thus more sensitive.

The disadvantages of the a ionizer systems are that personnel have a concern about sources in their work environment. This disadvantage can be overcome with education of personnel. The device also requires some government paperwork for tracking and regulation, and the replacement of the sources annually. This as not a financial issue but rather a logistical issue as the cost of replacement is comparable to the cost of maintenance required only of corona ionizers.

The objective of an ionizer is to eliminate surface charge on insulators and on isolated/ungrounded conductors. Practically speaking, the action of an ionizer is to drive the voltage on the surface of an object to be a small but non-zero value. Factors that affect this value are the fields emitted from the ionizer and the electric field of the earth.

EOS/ESD 3.1 defines a parameter called the Balance Voltage intended to be a measure of this value. It utilizes a device called the Charge Plate Monitor to measure this parameter. It employs a 150 mm. x 150 mm. plate as the sensor for the voltage. The standard specifies that it should have a capacitance of 20 pF. to ground. This capacitance drastically affects the response time of the device. It has been shown that small objects are driven to the same voltages as the CPM records but the response time of these small objects is much faster than that of the CPM plate. Thus, the HGA can experience effects due to fluctuations that would not be recorded by the CPM.

Measurements have been made by several groups of the residual ESD sensitivity to which HGA assemblies are subjected by AC and DC ionizers by recording the discharge current when an isolated HGA is discharged through a grounded current probe. This measurement is a direct measurement of the ESD threat because it directly measures a CDM (charged device model) discharge of a real product in a real situation. In this investigation, the previous work is reproduced with an increased bandwidth and with shorter probe leads which provide lower inductance and hence are expected to provide shorter and higher amplitude pulses, representing a more realistic view of actual CDM discharges of HGA structures. See Figure 3.

Figure 3. Apparatus for measuring CDM discharges of an HGA

The measurements involved a LeCroy model LC584AL digital oscilloscope with a bandwidth of 1 GHz and a sample rate of 8 Gsamples/sec. And a Tektronix CT-1 current probe with a bandwidth of 1 GHz (composite oscilloscope/probe bandwidth of 707 MHz). A typical CDM waveform obtained by discharging the paddle card of an HGA to ground is shown in Figure 4.

The signal has a rise time of well under 1 nsec. (~500 psec.) with a ground lead (see Figure 3) of <2 cm. In contrast, a similar signal with a slower (500 MHz bandwidth) oscilloscope and a rather long ground lead (~1 m.) is shown in Figure 5.

Figure 5. A CDM pulse from a HGA as measured with a large series inductance

For the purposes of comparison, we were able to gain access to state-of-the-art equipment to check the validity of our setup. A CDM pulse off of an HGA was recorded with a 2 GHz bandwidth oscilloscope and a 2 GHz bandwidth current probe. The resulting waveform is shown in Figure 6.

The rise time of the pulse is 380 psec. Comparing the wave shape in figures 6 and 8 shows little difference (~20% in rise time) so that the oscilloscope/probe combination employed was reasonable for the measurements, providing accurate (~10-20%) conclusions about CDM peak currents and energy dissipation in the head.

An apparatus was designed to allow HGAs to be placed under the influence of an overhead blower. The blower was mounted 36" above a dissipative work surface and any Balance voltage measurements were made 6" (150 mm) above the worksurface as per EOS/ESD 3.1. The heads were discharged by a short (<1 cm.) wire to ground and the resulting current pulse was recorded using a Tektronix CT-1 current probe.

The AC Ionizer

One AC overhead ionizer was used for the test. A CPM recorded the balance voltage as 0 V. Fifty discharges from the HGA to ground were recorded with the HGA on an insulated platform 24" off of the worksurface. Some of the current pulses were positive and others were negative. They were of varying amplitude but in general they were surprisingly large. Fifty discharges are shown in the top trace of Figure 7. Two typical discharges, one positive and one negative are shown in the lower traces. The vertical sensitivity of the traces is 5 mA/division.

Figure 7. Multiple CDM discharges from an HGA under an AC ionizer

As can be seen, the amplitude of the discharges vary dramatically and are of both polarities. Figure 8 shows a histogram of the amplitudes of the events. It shows that two peaks, one corresponding to the positive swing of the ionizer and the other corresponding to the negative swing.

The DC Ionizer

In order to estimate the effects of a DC ionizer on an HGA assembly, discharge measurements were made with Balance Voltages of –20 V, -10 V, +10 V and + 20 V. A histogram of the current amplitudes for each Balance Voltage was generated in order to calculate the mean and the standard deviation of the data set. Two such histograms are shown in Figure 9. In Figure 10, the means and standard deviations are plotted so that the performance of the system can be estimated at 0 V Balance Voltage.

The data in both figures clearly show a variation which is quite extreme and very different from the histogram shown in Figure 8.

Figure 8. Histogram of CDM current amplitudes under an AC ionizer

The variation shows that although the ionizer is balanced to an offset of 0 V or to 10 V or to any other value, the fluctuations in the ionization process are large enough that the ionizer will only be balanced on the average. It is capable of moving off of the zero point by a few volts of CPM voltage even though the CPM is too slow to respond to the variations. Since the ionizer is controlled by a circuit with an averaging time constant , the ionizer can only be expected to remain at its set point when averaged for that length of time. Since a CPM is an inherently slow device, it reads a stable value, and will show zero reading for a balanced ionizer in spite of fluctuations as seen in Figures 9 and 10.

Figure 9. Histogram of CDM discharge pulses for a DC ionizer set to a Balance Voltage of ±10 V

Figure 10. Extrapolating the CDM discharge current amplitudes ot zero balance voltage

In contrast, the AC ionizer shows a two peaked distribution that is typical of a sinusoidal driving signal. Because the signal is varying in time, it will show an amplitude histogram that is determined by the 50/60 cycle driving signal. .This effect is shown in Figure 11. It is an arc cosine distribution. This is the theoretical amplitude distribution based upon a sine wave which is randomly sampled. The dual peaked nature of the distribution looks much like the real data shown in Figure 8.

A similar experiment was done using an alpha ionizer. Again, the HGA was placed at a height of 24" (60 cm) above the work surface with the alpha overhead ionizer at a height of 36". After many attempts to measure a CDM discharge, it was concluded that no such discharge occurs. See Figure 11.

Figure 11. A null signal representing the absence of CDM discharge of an HGA under an alpha ionizer

Discussion and Conclusion

There are many attributes of an ionizer that must be considered in the selection of the appropriate one. These factors have been discussed above. For the purposes of the discussion below, only the ability of the ionizer to provide protection to the delicate heads is considered. The AC ionizer is clearly misleading when interrogated by a CPM. It exhibits considerable voltage swing that is not measured as a result of the limited bandwidth of the instrument. The DC ionizer when properly adjusted produces less of a wander than the AC device. The wander is expected to be a result of the roll off in the control circuit of the ionizer as required to establish a low enough noise level to maintain control of the balance. The Alpha ionizer is clearly the best choice when the issue of RSD protection is the only consideration.