Indoor Air Quality
Indoor Air Quality (IAQ) issues in a house arrive from a large variety of sources: Smoking is by far the worst cause of bad indoor air, which is why it is banned in most public buildings. Cooking is often one of the next things on the list of causes for bad indoor air. Did you remember to turn on the range hood last time you cooked, or was it simple too noisy or worse yet, a recirculator type. All the cleaners, soaps, shampoos, and other household chemicals definitely have an effect on indoor air quality. Soil gases like Radon. Pets of all variety may shed or have dander (although cat dander is one of the worst). Even the materials the house and furniture are made of (particle board, OSB, carpeting, paints & stains, etc.) can off gas (often formaldehyde). That new car smell that everyone knows, it is the off gassing (bad stuff) of various material (plastics mostly) that the car is made of, would you want to live in that environment very long, certainly not. Those people with allergies, asthma, or otherwise have a compromised lung function suffer the most from these problems. The longer people are exposed to bad air, the worse their problems can become. Here is a guide that I found that covers them in a basic way - Indoor Air Quality Guide. Below is a more complete discussion of some of typical areas of concern.
- General Solution
- Cooking
- Radon
- Volatile Organic Compounds (VOCs)
- PM2.5 (Particulate Matter)
- Carbon Monoxide
- Mold
The General Solution
There are two method to reduce the amount of these pollutants in your home. Used together they will minimize your exposure and reduce the possible health effects.
The first is to simple reduce the amount of pollutants that we bring into our houses. Sometimes this is easy, like not burning candles in the house or not using an unvented heater (such as a kerosene fired heater) indoors. Other times it may take more effort on our part, like trying to only use low-VOC carpeting or cleaning with products that have fewer chemicals in the ingredients. Still other times we cannot do anything about it, like if the PM2.5 levels are high outdoors, then they are going get into our houses. However, by reducing the amount that we bring into our houses it will be easier for the second method to be effective.
The second method is best summed up with the saying "The solution the pollution is dilution". This saying means that we need to bring in fresh air (outside air is usually less polluted then indoor air) to dilute the concentration of pollutants within our homes. There are a variety of methods to accomplish adding the fresh air. However, if we add too much fresh air, we take a penalty in the form energy cost. Too little saves us money, but can affect our health. There is a standard (ASHRAE 62.2) that deals with this issue and can be a good starting point for setting the proper amount of ventilation. An adjustable system would allow you to either increase the ventilation rate for better air quality or decrease to save some money (particularly if you are on vacation and no one is home or kids have gone off for college = few people home and less fresh air needed).
You may have noticed that I have not mentioned cleaning the air. That is because it is difficult and expensive to do if you have not started by reducing the amount of pollutants in the air. Using the two methods above should be good enough for most people. The extra filtration is really only needed for those that have special health concerns or you live in a very polluted area. However, your furnace air filter is designed to protect the blower motor and not really clean the air. In fact, putting a HEPA filter in the furnace is a good way to kill the blower motor (it is way too restrictive).There three ways to clean the air: first, there are special air filter packs (low static pressure loss) that can be added to the ducting that will clean the air. Second, a independent powered filter system can be piggybacked on to the return air to clean a portion of the air. However, the airhandler's fan needs to run a lot more for either of these two fixes to work. Third, a portable air cleaner system can be used and moved around to where you need it the most (usually the most cost effective solution).
Indoor Air Quality - Cooking
In non-smoking households, cooking is often the number one cause of air quality issues. Just think back to the last time you fried bacon in the morning and were still able to smell it at dinnertime. Gas stoves release carbon monoxide, formaldehyde, nitrogen dioxide, and particular matter. Electric stoves, ovens, and toasters release fine and ultrafine particles. High-temperature cooking produces acrolein, polycyclic aromatic hydrocarbons, and particulate matter.
The solution is not to stop cooking, but to ventilate by using a range hood that exhaust outdoors. You should always turn on the range hood before you even turn on the stove.
During a Home Performance Diagnostics, we will test you range hoods to see how much air it is moving. The minimum acceptable flow rate is 100 cfm. However, a better number would be 100 cfm/foot of range width for ranges against a wall and 150 cfm/foot of range width for ranges on islands (as recommended by the Home Ventilating Institute {HVI}). But don't get carried away and get a commercial range hood either, these often cause the house to depressurize, which can back-draft the water heater or furnace and introduce carbon monoxide into the house.
Interesting Links
NY Times - The Kitchen as a Pollution Hazard
Berkeley Lab - Pollution in the Home: Kitchens Can Produce Hazardous Levels of Indoor Pollutants
Environmental Health Perspectives - Take Care in the Kitchen: Avoiding Cooking-Related Pollutants-or- (Cached copy)