As you seal up your house for the winter, think about what you're sealing in as well as what you're sealing out.
All houses collect pollutants in indoor air: lead and asbestos from paint and insulation, radon from underground; ketones and aldehydes that vaporize or outgas from furniture and building materials; pesticides such as flea spray that are used or stored inside; volatile organic compounds from paints, solvents and glues; combustion contaminants from stoves, furnaces and fireplaces; breathable particulates, like house dust and tobacco smoke byproducts like the carcinogen benzo-(a)-pyrene.
Excessive moisture -- caused mostly by activities of people and pets -- encourages biological pollutants to join the mix: bacteria and viruses, molds, mildew and fungus.
Drafty houses collect less pollution, because the air is changed more regularly. But efforts to tighten up houses after the energy crisis of the '70s mean that indoor pollution is a growing concern.
Off all the indoor pollutants, the Big Three -- lead, asbestos and radon -- generally pose the most serious health risks. Each of them has its own abatement protocol, and in most cases, it's not something a homeowner can do. It requires a certified professional following legally mandated procedures.
The other pollutants can affect people in varying degrees -- however, the remedies for all of these are fairly simple: eliminate the sources and provide adequate controlled ventilation.
Here are the remedies for some specific pollutants:
*Chemical compounds -- Read the labels, ask questions, don't buy products that contain such chemicals. Eliminate existing sources, if possible. Increase ventilation and reduce humidity throughout the house. Buy antiques, or used furniture, and ventilate well after installing carpet. If someone in your household is sensitive and you can't eliminate all the sources, you may need an air-to-air heat exchanger, which ventilates the house without wasting energy.
*Pesticides and volatile organic compounds -- Store such materials in airtight spaces or outdoors; don't save leftover portions. Use substitute products, where available (latex or low-VOC paint instead of oil-based, for instance). If a label says "Use only with adequate ventilation," reconsider using the product indoors. If you have to use a pesticide indoors, for instance, a flea bomb, make sure you ventilate the space thoroughly afterward.
*Moisture -- Maintain windows, roofs, siding and foundation to eliminate leaks. Install outdoor-exhaust vents in bathrooms and kitchens. Leave doors open to promote indoor circulation. Restore transoms so they open; they were designed to facilitate air circulation and reduce moisture buildup.
*Combustion contaminants -- If you use a gas range, install a range hood that vents to the outside and run the fan while cooking. In wood stoves and fireplaces, use only seasoned wood; clean flues yearly to reduce creosote buildup. Make sure there is enough fresh air for combustion. Sometimes that means opening a window near the heat source; in any case, allowing the fire to feed on already heated room air is wasteful. (Some newer wood stoves and fireboxes are designed to use an outside air source.) Adjust heating equipment, especially gas and oil devices, so it burns properly. Make sure flues are cleaned. Some experts are recommending separate furnace rooms with a direct source of outside air for fossil-fuel-burning systems. (Vents and combustion devices may need sources of outside air because overventilation in a supertight house can create negative air pressure. That leads to backdrafts, which at the least may prevent a fireplace from drawing properly and at worst may prevent ventilation of combustion gases.)
Unvented kerosene heaters are banned in many areas; where they're not banned they should still be avoided, as they cause moisture problems as well as combustion contaminant problems.
*Smoking and particulates -- Stop smoking. You and everyone around you will lead a healthier life. If you refuse to stop, smoke outside. Particulates can be filtered out of circulating air. Different particulates require different levels of filtration. If someone in your house is sensitive, you may need to filter for the very smallest particles.
How aggressively you pursue these remedies may depend entirely on how sensitive your household is. Some people never have an inkling, for instance, that there's formaldehyde in their carpets; some people become ill from scant exposure.
If someone in your family is having a lot of unexplained illnesses, you might want to check for indoor pollutants. Your local utility company or fuel supplier may be able to help you check for high levels of combustion contaminants. There are test kits for formaldehyde, carbon monoxide and nitrogen dioxide. If you've followed all the remedies and still think you have a problem, you may want to consult a local health department, industrial hygienist, air-quality testing lab, or a good home inspector.
Next: Controlling humidity.
Mr. Johnson is construction manager for Neighborhood Housing Services of Baltimore. Ms. Menzie is Home Editor of The Sun.
If you have questions, comments, tips or experiences to share about working on houses, write to us c/o HOME WORK, The Sun, 501 N. Calvert St., Baltimore, Md. 21278. Questions of general interest will be answered in the column; comments, tips and experiences will be reported in occasional columns.