California Indoor Air Quality Program

There is no simple way of knowing short of learning about the possible types of indoor contaminants and investigating how much of each is in your house.  While there are no clear rules, different indoor pollutants tend to be higher in different kinds of homes. 

Newer homes tend to be built more tightly, to have less ventilation (unless they have built in, automatically operating ventilation systems – these are rare, but the new ASHRAE 62.2 (2010) and CA Title 24 (2010) now require minimum ventilation for newly built houses), and to have higher indoor build-up of various contaminants emitted by materials in the house.  Newer or remodeled homes also tend to have higher emissions of chemicals from surfaces and materials, although these diminish over time after construction or refinishing. 

Older homes, although they tend to be much "leakier" in terms of air flow, and thus have more ventilation, may be somewhat more likely to have moisture and mold problems. 

Homes with unvented gas furnaces are more likely to have higher levels of combustion emissions inside, as would homes with gas stoves and ranges without outside exhaust fans or with fans that are not used while cooking.  Homes that have bathrooms without exhaust fans will be more likely to develop excess moisture and mold unless ample ventilation is provided consistently by opening windows or doors during bathing.

Good information on keeping a healthy home and avoiding problems is available from the U.S. Housing and Urban Development (HUD) Agency at
Seven Tips for Keeping a Healthy Home
National Center for Healthy Housing
Help Yourself to a Healthy Home

If you have a problem with the air in your home, some approaches to reducing harmful indoor exposures include:

Removing the source of the problem – This is the best and most efficient way to solve indoor air problems.  Remove, replace, or seal the source of an indoor contaminant.  For instance, avoid

• indoor smoking,
• the use of toxic or odorous solvents or other chemicals for hobbies or cleaning,
• charcoal heaters,
• formaldehyde-emitting wood products or furniture, and
• stored fuel.

Ventilation – If you have indoor sources of a contaminant or moisture, it is most efficient to exhaust the air close to where the contaminant is produced, such as by using local exhaust fans in kitchens and bathrooms during cooking and bathing.  For contaminants that are more widely distributed in the house, and whose specific sources cannot be removed, general ventilation through windows or doors or a mechanical ventilation system can help reduce indoor concentrations.

There are relatively few explicit legal standards, at federal, state, or municipal levels, for potentially harmful indoor air exposures in homes.  Regulatory policies have focused more on outdoor air and workplaces.  However, some standards and codes do exist:

Chemicals – Some chemicals have general exposure guideline levels set by California (California Air Toxics Program) or the federal government (Technology Transfer Network, Air Toxics Web Site).  There are also national and some state standards for chemical exposures in workplaces.

Formaldehyde – There are no specific standards on formaldehyde exposures in homes, but California has standards for composite wood products limiting the amount of formaldehyde that may be emitted; the first phase became effective January 1, 2011; see Airborne Toxic Control Measure (ATCM) to Reduce Formaldehyde Emissions from Composite Wood Products.

Pesticides – There are no indoor standards but pesticides are restricted by U.S. Environmental Protection Agency regulations for use in specific applications and for use in specific ways; see Pesticides: Topical & Chemical Fact Sheets and Pesticides.

Asbestos – There are no specific standards on asbestos exposures in homes, but regulations exist on handling existing asbestos-containing materials and on the asbestos content of products.

Mold – Few standards exist for mold.  There are no U.S. Environmental Protection Agency regulations or standards for airborne mold contaminants.  Under the federal Occupational Safety and Health (OSH) Act, the General Duty clause requires that workplaces be free from recognized hazards that are causing or are likely to cause serious physical harm.  There is a regulation for mold in California workplaces (General Industry Safety Orders and General Sanitation Requirements for Mold).  California passed the Toxic Mold Protection Act of 2001, but it has not been implemented (for reasons outlined in a Report to the California Legislature, Implementation Update 2005). 

A few cities have enacted ordinances related to mold, such as San Francisco: mold is considered a legal nuisance, putting it into the same category as trash accumulation or an infestation of vermin.  Tenants (and local health inspectors) can sue landlords under private and public nuisance laws if they fail to clean up serious problems.  See Mold in Rentals.

Ventilation rate – Few standards regulate the amount of outdoor air ventilation a building provides.  Building codes generally determine how much ventilation a building must be designed to provide, but do not regulate the actual amount of outdoor air delivered after occupancy.  California workplaces, however, must comply with the Minimum Ventilation Standard of the Department of Industrial Relations.

Tobacco smoke/Environmental tobacco smoke (ETS)/Secondhand smoke – There are many regulations restricting tobacco smoking indoors in workplaces and commercial buildings, but generally none that apply to residences, although there may be some for multiple-occupant buildings.  Compilations of smoking bans are available for the U.S. (List of Smoking Bans in the United States) and worldwide (List of Smoking Bans by Country).

Carbon monoxide – There are no legal standards in California for indoor carbon monoxide (other than workplace exposure limits), but a state bill (SB 183, the Carbon Monoxide Poisoning Prevention Act of 2010)  requires carbon monoxide monitors in any home with an attached garage, a fireplace, or that is heated by oil or other fossil fuels – in new dwellings beginning in July 2011, and in existing dwellings beginning January 2013 (see New law to require home carbon monoxide detectors).