How to locate sources of indoor air pollution caused by appliances, HVAC equipment, and household chemicals and solvents. Control methods and health effects are also discussed.
More people are becoming concerned with indoor air quality (IAQ) and the potential health risks associated with indoor pollutants. Indoor pollution sources that release gases or particles into the air are made worse by inadequate ventilation. High temperature and humidity levels can also increase concentrations of some pollutants.
There are many sources of indoor air pollution in any home. These include combustion sources such as oil, gas, kerosene, coal, wood, and tobacco products; building materials and furnishings such as asbestos-containing insulation, wet or damp carpet, and cabinetry or furniture made of certain pressed wood products; products for household cleaning, home repairs, personal care, or hobbies; central heating and cooling systems and humidification devices; and outdoor sources such as radon, pesticides, and outdoor air pollution.
Any single source of indoor air pollution can be made better or worse depending on several factors such as age, amount of use, and how well it has been maintained or serviced. For example, an improperly adjusted gas stove can emit significantly more carbon monoxide than one that is properly adjusted. Items which are not usually referred to as a pollution source may increase the level of indoor pollution such as air fresheners and health and beauty products. High pollutant concentrations can remain in the air for long periods after certain activities or use of cleaning chemicals.
Indoor Pollution Sources
Pollutant Sources and Control Methods
Pollutant - Formaldehyde - Colorless gas with strong odor
Source - Various construction materials, including particleboard, interior paneling and drapes
Health Effects - Eyes, nose and throat irritation
Control - Substitute oriented strandboard (OSB) and exterior-grade plywood for particleboard. Seal particleboard with low VOC vapor proof sealers and paint or varnish in cabinets and closets on subflooring. Increase ventilation rates.
Pollutant – Radon -Odorless, colorless radioactive gas
Source - Soil beneath and around the house foundation
Health Effects - Believed to be the cause of 5 to 10 percent of all lung cancer.
Control - Seal floor drains, sump pits and all cracks, joints and penetrations through basement walls and slab. Ventilate crawl space and seal subfloor joints and penetrations. Depressurize the gravel bed beneath slab or isolated the basement from the rest of the house and pressurize it with air drawn from the floors above.
Pollutant – Carbon Monoxide - Colorless, odorless gas
Source - Kerosene heaters, wood-burning appliances, unvented gas appliances, attached garages, blocked chimneys and malfunctioning furnaces
Health Effects - Nausea, headaches and blue fingernails. Severe poisoning can cause brain damage in fetuses and can be fatal
Control - Provide outside combustion air feed to the firebox of all wood-burning appliances. Install tight-fitting doors on fireplaces and wood stoves. Vent gas ranges directly to the outside. Provide make-up air for exhaust fans. Use induced-draft or sealed-draft hot water heaters and furnaces.
Pollutant – Nitrogen Dioxide - Has odor when present in large quantities.
Source - Kerosene heaters and unvented gas appliances
Health Effects - Lung damage and increased potential for lung disease after long exposure.
Control – Same control methods as for Carbon Monoxide (CO)
Pollutant –Suspended Particulates -Particles suspended in the air that can be inhaled
Source - Tobacco smoke, wood smoke, unvented gas appliances, kerosene heaters, asbestos construction materials, cooking, dust, pets, pollen.
Health Effects - Eye, nose and throat irritation, lung cancer, emphysema, heart disease, bronchitis, respiratory infections
Control - Avoid smoking inside. Ensure wood-burning appliances and flues do not leak. Properly vent combustion appliances to the outside. Provide outside combustion air feed to the fireboxes of all wood-burning appliances. Install tight-fitting doors on fireplaces and wood stoves.
Increase ventilation rates. Use medium efficiency pleated fabric filters or HEPA filters in furnace or air handling unit and change them regularly. Inspect air condition and heating ductwork and clean if needed. UV-C lights may be installed inside the air handling unit to destroy organic materials and viruses.
Pollutant – Moisture - Humidity
Source - Ground water entering through the foundation, cleaning, bathing, washing and respiration. Inadequate moisture removal of air conditioning equipment. Concrete slab condensation during air conditioning season.
Health Effects - Causes growth of micro-organisms, increases release of formaldehyde.
Control - Maintain drainage beneath the foundation and provide drainage at the foundation's perimeter. Seal beneath the foundation with a polyethylene barrier. Provide adequate ventilation. Vent clothes dryer directly to the outside. Pump air conditioning condensate to the outside. Use dehumidifiers in damp basements. Inspect carpeting installed directly on concrete slabs and remove if stained or damaged.
Pollutant – Organic Solvents
Source - Household cleaners and solvents in paints and caulking
Health Effects - Eyes, nose and throat irritation, can affect central nervous system
Control - Use solvent-based materials only in well-ventilated areas. Substitute water-based paints and caulking for solvent based products. Use building materials with low VOC ratings.
Indoor Pollution Control Diagram
If too little outdoor air enters a home, pollutants can accumulate to levels that can pose health and comfort problems. Newer homes are built to reduce the amount of air leakage through the building envelope and usually have high-efficiency HVAC equipment that is ducted to the exterior of the home. Older homes are “leaky” and reduce the amount of outdoor air required. However some weather conditions can reduce the air leakage of drafty, older homes so indoor pollutants can still build up to unhealthy levels.
Outdoor air enters and leaves a house by: infiltration, natural ventilation, and mechanical ventilation. In a process known as infiltration, outdoor air flows into the house through openings, joints, and cracks in walls, floors, and ceilings, and around windows and doors. In natural ventilation, air moves through opened windows and doors. Air movement associated with infiltration and natural ventilation is caused by air temperature differences between indoors and outdoors and by wind.
Mechanical ventilation devices can also be installed in individual rooms to exhaust indoor air to the outside such as bathrooms and kitchen exhausts. Air handling systems may also use outdoor air intakes to continuously remove indoor air and distribute filtered and conditioned outdoor air to areas throughout the house. The rate at which outdoor air replaces indoor air is described as the air exchange rate. When there is little infiltration, natural ventilation, or mechanical ventilation, the air exchange rate is low and pollutant levels can increase.
Indoor Air Pollution and Health
Health effects from indoor air pollutants may be experienced immediately after exposure or several years later.
Immediate effects may show up after a single exposure or repeated exposures. These include irritation of the eyes, nose, and throat, headaches, dizziness, and fatigue. Such immediate effects are usually short-term and treatable. Often the treatment is simply eliminating the person's exposure to the source of the pollution, if it can be identified and moving the person to a place where they can breathe fresh air. Symptoms of some diseases, including asthma, hypersensitivity pneumonitis, and humidifier fever, may also show up soon after exposure to some indoor air pollutants.
Age and preexisting medical conditions are two important factors to the immediacy of any adverse health reactions. Sometimes the effect depends on individual sensitivity, which varies greatly from person to person. Some people can become sensitized to biological pollutants after repeated exposures, and it appears that some people can become sensitized to chemical pollutants as well.
Certain immediate effects are similar to those from colds or other viral diseases, so it is often difficult to determine if the symptoms are a result of exposure to indoor air pollution. For this reason, it is important to pay attention to the time and place symptoms occur. If the symptoms fade or go away when a person is away from home.
Some health effects may show up years after exposure has occurred or only after long or repeated periods of exposure. These effects may include some respiratory diseases, heart disease, and cancer.
While pollutants commonly found in indoor air can be responsible for many harmful effects, there is much debate about what concentrations or periods of exposure are necessary to produce specific health problems. This uncertainty combined with individual reactions to exposure to indoor air pollutants makes the problem even more challenging. It is prudent to try to improve the indoor air quality in your home even if symptoms are not noticeable.
Measuring Pollutant Levels and Weatherizing Your Home
What if You Live in an Apartment?
Volatile Organic Compounds (VOCs)