Asthma Indoor Air Pollution

Indoor air can often prove a greater threat to asthmatics than the air outdoors.

Pollutants generated in a “sealed” indoor environment commonly build up to dangerous levels. Studies by the Environmental Protection Agency (EPA) report that levels of indoor pollutants tend to be two to five times (and in certain cases 100 times) higher than levels of outdoor pollutants. Furthermore, air conditioning and heating systems are notorious for producing abrupt changes in temperature that can very easily trigger an asthma attack.

The EPA report also concluded that “poor indoor air quality” was the fourth largest threat after “volatile organic compounds, lead dust and asbestos.”

Although total elimination of indoor air pollution is not always possible (or feasible), a great deal can be done to improve indoor air quality. The use of HEPA, or high efficiency particulate air, filters and air purifiers in the home can contribute to the reduction of pollutants that can be blown in through ventilation systems.

Description Effect on Indoor Air Quality
HEPA filters HEPA filters have a minimum particle removal efficiency of 99.97% for all particles of 0.3 micron diameter and higher. This size covers most pollens, mold spores, animal hair and dander, dust mites, bacteria, smoke particles and dust. Generally accepted as an essential piece of equipment for the control and management of indoor pollution, HEPA filters are used extensively in medical and industrial environments. They are now commonly available in residential air cleaners.
Air purifiers Air purifiers are classified according to the technology they use to remove different-sized particles from the environment. They can be either mechanically or electronically operated; certain versions use a chemical process (e.g., ozonization) to “purify” the air. Very effective at pollutant removal and come in a variety of sizes.
Large room unit air purifiers Equipped with powerful filters or “collecting” plates, some large units use electrostatic precipitation. Highly effective at removing pollutants (especially smoke and dirt) from large rooms. Generally considered more effective as single room units than as fixed central air filters.
Tabletop air purifiers Equipped with small panels of dry, loosely packed, low-density fiber filters and a high velocity fan. Although relatively inexpensive and generally a good value, caution is required when selecting tabletop purifiers. Make sure that the specifications match your requirements (e.g., Can the device cope with very small particles noted for their ability to penetrate the lungs, thus triggering an asthma attack?).
Air filters (efficiency is usually measured according to the size of particle that the device can remove) Air filters fall into two broad categories: central filtration systems (sometimes called “induct” systems) and portable units with fan attachments. Central system filters are installed in heating, ventilation and air conditioning systems (know as HVAC). Air filters can be mechanically or electronically driven, or a hybrid of both. Asthma sufferers are often advised to choose a HEPA type filter that is capable of trapping both very large and very small sized particles.
Specially designed vacuum cleaners (e.g., HEPA vacuum cleaners) Equipped with high spec pre-filter and filter systems, these sealed and allergen-free units are capable of removing and trapping indoor pollutants that normal vacuum cleaners don’t. These high-performance vacuum cleaners are recommended for their capacity to remove potentially dangerous triggers, such as bacteria and mold filled dust.


American Academy of Allergy, Asthma and Immunology. (updated 2004). Tips to remember: Asthma triggers and management.

American Lung Association. (updated 2002). Air Quality.

American Lung Association. (updated 2002). Home control of allergies and asthma.

American Lung Association Health House. (updated 2002). Indoor air quality.

Environmental Protection Agency. (updated 2002). Indoor air quality (IAQ).