Healthy Homes - Indoor Air Quality

About Combustion Gases/Carbon Monoxide

Every year about 500 people die in their homes from carbon monoxide poisoning. In some cases an entire family dies from this completely preventable death. What is carbon monoxide? It is a poisonous gas that interferes with blood’s ability to carry oxygen. Carbon monoxide is produced when a fuel is burned, such as natural gas, propane, fuel oil, wood, charcoal, and gasoline. In furnaces, boilers, water heaters, wood stoves, and fireplaces, carbon monoxide and other products of combustion are vented to the outside through the chimney. Barbeque grills and gasoline engines vent directly to the area around them. Gas-fired kitchen ranges vent to the outside, but only if an exterior-ducted exhaust fan does this mechanically.

A carbon monoxide problem occurs when a combustion appliance is not maintained properly. Heating systems, chimneys, and flues should be inspected and cleaned annually by a qualified technician. Things like a cracked heat exchanger or blocked chimney can be taken care of before they cause serious problems.

Always make sure flues are open when a fireplace is in use. Don’t use ovens or gas ranges to heat your home, even during an emergency. Never burn charcoal inside a home, cabin, recreational vehicle, camper, or any enclosed space. Choose vented fuel-burning appliances whenever possible. If you must use an unvented space heater, make sure the area you use it in is well ventilated.

While carbon monoxide alarms are not substitutes for combustion appliance maintenance, they can provide warnings in dangerous situations. Make sure the alarms you purchase meet Underwriters Laboratories (UL) standards, have a long-term warranty, and can be easily self-tested and reset to ensure proper functioning. The best place for a carbon monoxide alarm is near sleeping areas.

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COMBUSTION POLLUTANTS OF MOST CONCERN

Specific combustion pollutants that are of most concern in your home:

• Carbon monoxide - an odorless gas that can kill
• Nitrogen dioxide - gas that can damage the respiratory tract
• Sulfur dioxide - gas that irritates the eyes, nose, and respiratory tract
• Particulates - tiny particles that make up smoke and irritate the eyes, nose, and throat
• Water vapor - excess moisture that can lead to mold and rot of the house structure

SOURCES OF COMBUSTION POLLUTANTS

Combustion pollutants in the home come from a variety of sources:

• Heating or cooking appliances that burn fossil fuels:
• Gas, oil, coal, or wood furnaces or boilers
• Gas or oil water heaters
• Gas or kerosene space heaters
• Fireplaces
• Wood or coal stoves
• Gas ranges and ovens
• Gas clothes dryers
• Tobacco smoking
• Exhaust from automobile engines operating in attached garages
• Other equipment with internal combustion engines, such as lawn mowers or generators
• Other combustion/burning activities, such as welding or soldering
• Gas or charcoal grills and hibachis

COMBUSTION POLLUTANTS MAY CREATE AIR QUALITY PROBLEMS

Combustion pollutants are more likely to create air quality problems when:

• Pollutants from combustion equipment are not exhausted to the outside of the home
• Combustion equipment is not maintained in good working order
• Combustion equipment is not regularly inspected for safe operation
• Air pressure indoors is lower than outdoors, preventing safe exhaustion of combustion pollutants
• Tobacco smoking is permitted in the home
• Every piece of equipment or activity in the home that involves combustion or burning has the potential to introduce combustion air pollutants.

HEALTH EFFECTS

Health effects from exposure to combustion pollutants vary from very mild to lethal. Typical health effects are:

• Headaches
• Dizziness
• Sleepiness
• Nausea
• Irritated eyes
• Breathing difficulties
• Respiratory problems (i.e., coughing)
• People with allergies, asthma, or chronic respiratory or heart problems are particularly susceptible to health effects from combustion pollutants. It is important to note, though, that these health effects can have many other causes as well.

COMBUSTION POLLUTANTS

Combustion pollutants in indoor air may be the source of health problems if:

• Symptoms occur only in the home
• Symptoms improve when you leave the home
• More than one person in the home has similar symptoms
• Your home has one or more of the five air quality problems above

WHAT IS CARBON MONOXIDE?

The combustion pollutant carbon monoxide (CO) is of greatest concern because it can be fatal. Hundreds of people are killed each year by CO in their homes.

Carbon monoxide can build up in an enclosed space and it is odorless and colorless, so you may not be able to sense what is making you sick. Carbon monoxide reduces the ability of hemoglobin in the blood to carry oxygen. Health effects or symptoms of CO poisoning can be similar to other illnesses, such as the flu or allergies.

Lower doses of CO:

• Nausea
• dizziness
• weakness
• muscle ache

Higher doses of CO:

• Impaired judgment
• paralysis
• coma
• death

CARBON MONOXIDE BUILDUP

Carbon monoxide buildup typically occurs in one of several ways:

• Flues or chimneys from combustion equipment become blocked (such as by a bird's nest), disconnected, rusted, or broken. Therefore, combustion pollutants, high in CO, cannot be exhausted to the outside.
• A fuel-burning appliance, such as a furnace, has a cracked heat exchanger, allowing combustion gases into living spaces instead of being exhausted up a chimney or flue
• Unvented fuel-burning (such as kerosene or gas) heaters are operated in the home without adequate ventilation
• Charcoal cookers, grills, or hibachis (which produce high levels of CO) are operated in the home
• Gas ovens are improperly used for space heating
• Carbon monoxide from an idling car, lawnmower, or other engine in an attached garage enters the home
• Combustion equipment is poorly maintained and incomplete combustion occurs, which produces a high level of CO. Yellow flames are sometimes an indication that CO is being produced; blue flames means more complete combustion and fewer pollutants.
• Low indoor air pressure compared to the outside prevents adequate venting of natural draft combustion equipment, causing combustion pollutants to "spill" into the home in a condition known as backdrafting

BACKDRAFTING

Backdrafting occurs when there is negative pressure in the area where the combustion device is located. This means the air pressure inside the area is lower than the air pressure outside.

Negative pressure indoors can occur when there are duct leaks in the heating system, or when exhaust ventilation, such as from a clothes dryer or kitchen or bathroom exhaust fan, is greater than air replacement through infiltration or other means. This scenario is most likely to occur in "tight", well constructed, energy efficient homes that do not have controlled ventilation.

When there is negative pressure indoors, combustion by-products from conventional (natural draft) furnaces, water heaters, fireplaces, or similar equipment tend to spill into the room, or BACKDRAFT, rather than exhaust to the outside.

PREVENTION OF BACKDRAFTING

To prevent backdrafting of carbon monoxide and other combustion pollutants in your home:

• Keep all combustion equipment, flues, and chimneys in top working order
• Do not use an exhaust fan in the same area where a naturally-vented combustion appliance is operating
• Select closed combustion or draft-induced combustion equipment, or provide an outside air source for combustion appliances, especially in tightly constructed homes
• Do not implement air-tightening measures, such as caulking, weather stripping, insulation, or new/improved windows, without investigating potential impacts on the operation of combustion equipment

CARBON MONOXIDE ALARMS

Consider the installation of a carbon monoxide alarm with an audible warning. A CO alarm will alert you to dangerous, high levels of carbon monoxide, and give you time to vacate or ventilate the home. Depending on the type of CO alarm, it may not detect low levels of CO that can still make you ill.

A CO alarm does not replace regular maintenance, inspection, and safe operation of combustion equipment!

REDUCING COMBUSTION POLLUTION RISKS IN YOUR HOME

Reducing the risk of carbon monoxide pollution in your home involves many of the same steps as reducing your risk of all combustion pollution.

First...Keep all combustion equipment well-maintained and inspected for safety: Experts recommend combustion heating systems, such as furnaces and boilers, be inspected by a trained professional every year prior to the heating season for:

• Blocked or clogged openings to flues and chimneys
• Excessive production of carbon monoxide
• Cracked, separated, or disconnected flue pipes
• Dirty filters (clean or replace monthly)
• Rust or cracks in the heat exchanger
• Soot, corrosion, or creosote buildup
• Burner/flame adjustment
• Exhaust or gas odors

Always operate combustion equipment safely, according to directions, and for its intended purpose. For example, never use an oven or clothes dryer as a space heater, or never use a charcoal grill inside the house.

Have combustion equipment installed correctly by a trained installer and according to local safety codes

Second...Exhaust all combustion pollutants to the outside of the home:

• Avoid the use of unvented combustion appliances, such as kerosene or gas space heaters
• Do not disconnect vents on combustion appliances, even if it seems like a way to get extra heat in the winter
• Use an exhaust fan ducted to the outside to provide spot ventilation if a combustion appliance is not vented directly outside; always use an exhaust fan when operating a gas range or oven
• When purchasing new combustion appliances, look for sealed combustion units that use outside air for combustion and then exhaust it back outside; therefore, combustion pollutants are never mixed with room air

Third...Maintain an adequate pressure balance between the home and the outside:

• Provide an outside air source for combustion equipment
• Consider opening a window slightly when operating an exhaust fan

Fourth...Do not allow tobacco smoking in your home (See Secondhand Smoke)

MORE INFORMATION:

WHAT IS CARBON MONOXIDE?

Carbon monoxide (CO) is a gas produced when any carbon-based fuel is burned. The amount of CO produced depends mainly on the quality or efficiency of combustion. A properly functioning natural gas or liquified petroleum gas (LPG) burner produces little CO, while an out-of-adjustment burner can produce life-threatening amounts without any visible indications.

What really matters, though, is how this deadly gas is disposed of. If CO collects in an enclosed space, or if other conditions result in exposure to it, it can cause illness or death.

A big problem is that the gas itself is odorless and colorless, so it can collect in spaces without our being aware of it. Some types of fuel (wood, oil) produce other combustion products (with odors) along with CO, so there can be some warning. These other pollutants can be dangerous as well and may be produced even when CO levels are not harmful.

Proper maintenance of combustion appliances (furnaces, space heaters, ranges, ovens, gas water heaters, etc.) and their chimneys and flues is essential to preventing CO buildup indoors. It is important that service technicians test and adjust appliances using instruments that can measure CO productions. CO alarms can also aid in warning occupants of elevated CO levels. More information on CO alarms will be discussed towards the end of this presentation.

CARBON MONOXIDE IMPACT

According to the National Safety Council and the Centers for Disease Control and Prevention, about 500-1,000 people are killed in their homes each year by CO. It is likely that many more are harmed to some degree by this gas, but the extent is not known.

A recent research study revealed that heart patients' emergency room admissions had a small but significant correlation with changes in the outdoor levels of carbon monoxide. It was concluded that episodes of elevated outdoor CO can trigger emergencies in some heart patients exposed to this gas. It is possible that elevated indoor CO levels may likewise trigger problems in some heart patients. [Citation: Morris, et. al. Journal of Public Health, Volume 85, p 1361, October 1995.]

CO SOURCE - FUEL BURNING

Where does carbon monoxide come from? How does it get into the house?

There are many possibilities for carbon monoxide entry and accumulation in homes. Burning fuel for heating or cooking is the main source. Problems arise when combustion gases accumulate in buildings.

COMMON SOURCES OF CO IN HOMES

Accumulation of combustion gases usually happens when a blocked chimney, rusted heat exchanger, or broken chimney connector pipe (flue) prevents combustion gases from being exhausted from the home. CO can also enter the home from an idling car or other engine (generator or lawnmower) in the garage.

Another scenario involves backdrafting; sometimes when ventilation equipment (such as a range-top vent fan) is used in a tightly sealed home, reverse air flow can occur in chimneys and flues. An operating fireplace can also have significant interactions with the flue dynamics of other heating appliances and backdrafting may result.

Other common sources of CO include unvented, fuel-burning space heaters (especially if malfunctioning) and the indoor use of a BBQ (charcoal). CO is produced by gas stoves and ranges and can become a problem with prolonged, improper operation (for example, if these appliances are used to heat the home). A change in the gas flame's color can indicate a CO problem; if a blue flame becomes yellow, CO will be increased. However, some blue flames produce elevated CO levels as well, while some new appliances normally have a yellow flame.

HEALTH EFFECTS - SYMPTOMS

What sorts of problems are caused by carbon monoxide?
What symptoms are seen?
Can these symptoms warn victims that a problem exists?

CO bonds tightly to the hemoglobin in red blood cells, preventing them from carrying oxygen throughout the body. Levels of CO that can result from common household sources may cause nausea, dizziness, muscle aches, vomiting, and a general weakness throughout the body. These symptoms resemble the flu or food poisoning, and CO exposure is often mistaken for these illnesses. Larger CO doses can impair judgment, or the weakness becomes paralysis, which can be followed by coma or death.

CO victims must be removed from exposure as quickly as possible and require prompt medical attention. Because of the tight bond of CO to hemoglobin, recovery is not immediate when the victim is removed from exposure.

Carbon monoxide will usually affect all occupants of a household at the same time. This may be a good way of distinguishing it from the flu, but it is important to realize that CO poisoning also impairs judgment and such a realization may become difficult to attain.

INDOOR COMBUSTION APPLIANCES

While larger combustion appliances are designed to be connected to a flue or chimney to exhaust combustion products, some smaller appliances are designed to be operated indoors without a flue. Appliances designated as supplemental or "decorative" heaters (including most unvented gas fireplaces) are not designed for continuous use. To avoid excessive exposure to pollutants, never use these appliances for more than four hours at a time.

When operating unvented combustion appliances, safe practices must be carefully followed. Besides observing fire safety rules, make sure the burner is properly adjusted and there is good ventilation -- never use in a closed room, keep doors open throughout the house, and open a window for fresh air.

Never use outdoor appliances (such as BBQs or construction heaters) indoors. Do not use appliances such as ovens and clothes dryers to heat the house.

Inspect heating equipment. Make sure flues and chimneys are not blocked to reduce the chances of backdrafting in furnaces, fireplaces, and similar equipment. Inspect metal flues for rust; in furnaces, the heat exchanger should be checked for rust and cracks. Soot is also a sign of combustion leakage. When exhaust fans are used, open a nearby window or door to provide replacement air.

SELECTING A CARBON MONOXIDE ALARM

In recent years, CO alarms have become widely available in the consumer marketplace. When selecting a CO alarm, make sure it meets the stringent requirements of Underwriters Laboratories (UL), Inc. or the International Approval Service (IAS). These requirements are described in greater detail in the next overhead.

Modern CO alarms can provide warnings for even non-lethal levels of this dangerous pollutant, but alarms should not be thought of as "the end all, be all" to alert you to dangerous CO levels in your home. The U.S. Consumer Product Safety Commission recommends having at least one CO alarm in every home, placed outside all sleeping areas.

In considering such a purchase, make sure alarms have a long-term warranty, and can be easily self-tested and reset to ensure proper functioning. Consumer organizations such as Consumer Reports occasionally evaluate these devices. Look for the most recent articles on this subject.

Here are some general points to consider before buying a CO alarm:

Some inexpensive alarms consist of a card with a spot ("spot" detectors) that changes color in the presence of CO. The absence of an audible signal does not meet UL or IAS requirements for alarms; these devices do not provide adequate warning of CO.

CO alarms are a backup (NOT a replacement) for regular heater maintenance!

Battery-operated alarms are portable and will function during a power failure, which is when emergency heating might be used. Batteries must be replaced, although some alarms have long-life batteries that will last up to 5 years.

Line-powered alarms (110 volt) require electrical outlets, but do not need batteries. They will not function during a power failure. Some line-powered alarms have battery backups.

Some alarms have digital readouts indicating CO levels. Alarms with memories can help document and correct CO problems.

NEW STANDARDS FOR CO ALARMS

A new standard for CO alarms took effect in October 1998. The new standard changes the designation of CO units from "CO detectors" to "CO alarms." Alarms are now required to sound at CO levels of 70 parts per million (the old standard was 100 ppm) and are prohibited from sounding or indicating at levels below 30 ppm (some older units were more sensitive).

Alarms manufactured to these new UL and IAS standards give additional protection against acute, high levels of CO, but do not protect against CO levels below 30 ppm. When purchasing an alarm, consumers should look for one meeting the most current standards. Presently, alarms should bear the designation of either UL 2034 or IAS-696. Individuals with medical problems might consider using an additional detection device that has lower signaling capabilities.

Note to the Program Leaders: False alarms: good/bad news! Manufacturers and testing agencies continue to struggle with a balance of adequate sensitivity and false alarming. Occupants need to be extremely vigilant: Some CO alarms may still trigger when there is no problem. At the same time, some "nuisance" alarms turn out to be the real thing. Judgement needs to be used here: CO symptoms in any occupant means that CO exposure may exist. If there are repeated alarms, it may be necessary to vacate the home; otherwise have the home checked or use a new alarm. Do not ignore "false" alarms; find out whether there is a problem or the alarm is defective.

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FROM CORNELL UNIVERSITY, ITHACA, NY

Indoor air pollutants in low-income housing and in many child-care centers may put children at health risk

ITHACA, N.Y. — In areas prone to high radon levels, homes occupied by limited-resource households have significantly higher levels of radon than those occupied by higher income households, and some child-care centers have unsafe levels of radon, lead and mold, according to a new study at Cornell University.

“We found levels of pollutants in homes and child-care facilities that we should be concerned about,” says Joseph Laquatra, associate professor of design and environmental analysis in the New York State College of Human Ecology at Cornell. “Even low levels of exposure to some of these pollutants is dangerous, and if you have a child who lives in a home with high radon, lead and mold levels and then spends the day being exposed to those same pollutants in a child-care facility, that child may be at significantly higher risk for lead poisoning, cancer, asthma attacks and allergies.”

Laquatra, who conducted the study with colleagues Lorraine Maxwell and Mark Pierce, both in the Department of Design and Environmental Analysis with Laquatra at Cornell, will report these findings at the Ninth Annual International Conference on Indoor Air and Climate in Monterey, Calif., July 2.

The indoor environmental experts tested indoor air pollution levels in a representative sample of 328 houses and 75 child-care facilities in six nonmetropolitan counties (Chenango, Columbia, Essex, Franklin, Wyoming and Hamilton) in New York state.

They also found that the homes of lower income residents had higher levels of carbon monoxide, probably because 60 percent of the homes in the study had no functioning kitchen exhaust fan, the researchers said. In addition, 16 percent of the homes in the study had asbestos problems, and 10 percent had basement mold.

“Limited-resource households have disproportionate exposure to radon and other indoor air pollutants, most likely because of lower quality housing and housing deficiencies that create pollutant pathways, such as foundation cracks and dirt basement floors, as well as chipped paint, friable asbestos and leaking combustion equipment,” Laquatra says.

“Lead poisoning in children leads to lowered intelligence and behavioral problems. Mold is a trigger for allergies and asthma, both of which lead to school and work absences, productivity losses and increased health costs,” Laquatra says. Exposures to asbestos, carbon monoxide and radon can lead to early death.

“Health officials and policy-makers agree that indoor air pollutants pose serious health risks, and they expend considerable resources to raise public awareness of these risks. But for low-income households, resources for pollutant abatement are negligible, which generates a dilemma for public policy,” Laquatra says.

A follow-up study at Cornell is examining the effectiveness of teaching low-income household members practical management strategies to minimize their risks of exposure to indoor air pollutants.

The study was supported, in part, by a U.S. Department of Agriculture Hatch Grant.

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