[from "The Inside Story: A Guide to Indoor Air Quality" by the CPSC]

Indoor pollution sources that release gases or particles into the air are the primary cause of indoor air quality problems in homes. Inadequate ventilation can increase indoor pollutant levels by not bringing in enough outdoor air to dilute emissions from indoor sources and by not carrying indoor air pollutants out of the home. High temperature and humidity levels can also increase concentrations of some pollutants.

Pollutant Sources

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 as diverse as deteriorated, asbestos-containing insulation, wet or damp carpet, and cabinetry or furniture made of certain pressed wood products; products for household cleaning and maintenance, personal care, or hobbies; central heating and cooling systems and humidification devices; and outdoor sources such as radon, pesticides, and outdoor air pollution.

The relative importance of any single source depends on how much of a given pollutant it emits and how hazardous those emissions are. In some cases, factors such as how old the source is and whether it is properly maintained are significant. For example, an improperly adjusted gas stove can emit significantly more carbon monoxide than one that is properly adjusted.

Some sources, such as building materials, furnishings, and household products like air fresheners, release pollutants more or less continuously. Other sources, related to activities carried out in the home, release pollutants intermittently. These include smoking, the use of unvented or malfunction-ing stoves, furnaces, or space heaters, the use of solvents in cleaning and hobby activities, the use of paint strippers in redecorating activities, and the use of cleaning products and pesticides in housekeeping. High pollutant concentrations can remain in the air for long periods after some of these activities.

Amount of Ventilation

With too little fresh air, pollutants can accumulate to levels that can pose health and comfort problems. Without the introduction of sufficient outside air, "airtight" (thermal efficient) office environments may have higher pollutant levels than in older, less efficient buildings. 


Consumer Product Safety Commission,
Environmental Protection Agency

Frequently Asked Questions - Indoor Air Quality

Q.  I get sleepy at my desk every afternoon, my eyes itch and I get the sniffles or headaches, usually around 2:00 p.m. Could it be an air quality problem?

A.  Perhaps.  It's also possible your stomach is diverting blood from your brain in order to digest your lunch, causing your sleepiness. 

If lighter meals and brisk walks during your lunch break don't improve things, testing for carbon dioxide (CO2) may be indicated.  CO2 is a normal consituent of human breath.  In an occupied office building, CO2 levels are normally between 400 and 700 parts per million (ppm).  Heavy occupancy and/or inadequate ventilation can push CO2 levels to more than 1000ppm, above which complaints of itchy eyes, watery nose, and possibly headaches, may occur (severe headaches are sometimes an indicator of carbon monoxide - see below).  Carbon dioxide is not dangerous until it reaches extremely high levels approaching 5,000 ppm.

Q:  Someone said they can smell asbestos in my building - what shall I do?

A:  Asbestos is a mineral and does not have an odor.  If your building is more than 20 years old (pre-1990) and you're concerned that you're working near asbestos, ask to see a copy of the survey report.  If the material you're concerned with isn't listed (or if there is no report), ask to have it tested.  In California, any material with greater than (>) 0.1% asbestos is considered hazardous.

Q.  Is there a single test that can tell me what might be contaminating the air I'm breathing?

A.  No.  There are separate tests for literally hundreds of possible airborne contaminants, each with its own sampling media and sampling protocol. 

However, when complaints are non-specific - but widespread and persistent - there are a few initial, general tests that often prove useful:

     Volatile Organics (VOCs), a measure of more than 30 airborne chemicals from a variety of processes.

     Q-Trak, a machine that can measure and record CO, CO2, temperature and relative humidity across a 24-hr. period

     Airborne Mold Spores - particularly useful when complaints reference allergens or allergic symptoms

     Fibrous Dust - including asbestos and fiberglass.

     Nuisance and Respirable dust - respirable dust can cause problems by penetrating and lodging deep into the lungs. 

     Ultra-Fine Particles (UFPs) - Less than one micron in diameter, UFPs are created by certain copiers and laser printers.