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Now that your house is drum-tight, what about indoor smog?

Energy-efficient housing may be low on fuel costs but high in household smog. The buildup of gases, particulates, and vapors can create a hazard in overinsulated houses where there is too little air exchange between indoors and outdoors. Indoor air may become loaded with pollutants in concentrations which, if found outdoors, could be illegal.

Indoor pollutants come from three sources: combustion, construction materials , and chemicals.

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Combustion pollutants. Because of their widespread use, combustion appliances (gas appliances, kerosene heaters, wood stoves, and the like) represent the largest potential source of indoor air contamination.

To lessen the hazards of indoor pollution from gas appliances, increase the air-exchange rate, crack a window or door while cooking, or frequently air out the house. Exhaust fans are a good way to ventilate gases at their source. Air-to-air heat exchangers provide a constant source of fresh air without sacrificing heating dollars.

Proper maintenance of gas appliances is essential. An annual inspection will ensure that pilot lights and cooking flames are burning properly, vents are clear of debris, and all pipes are free from holes and cracks.

Kerosene heaters have long been controversial. The American Insurance Association (AIA) recommends that a homeowner allow at least 200 cubic feet of air space in the room for each 1,000 BTU of heat generated. Total heat output should never exceed 25,000 BTU per house. In addition, the AIA suggests cracking an outside window at least an inch and opening the doors to adjacent rooms while the heater is in use.

Fireplaces also can pollute indoor air. The damper should be fully open while the fireplace is in use. A window should also be partly open to provide ventilation as well as enough air for the fire to burn properly. What is burned in the fireplace also affects the quality of indoor air. Burning the Sunday comics may release a dose of arsenic vapor into the room, and treated wood may spew out an assortment of chemical fumes.

Construction pollutants. Certain types of particleboard, fiberboard, plywood, carpeting, draperies, and insulation may give off formaldehyde gas. The safety of urea-formaldehyde insulation, in particular, has been a subject of debate for years.

While there is no consensus on how much formaldehyde gas constitutes a hazard , the US Consumer Product Safety Commission recommends 0.1 parts per million as an acceptable level.

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The 3M Company sells a do-it-yourself testing kit for about $35. (For more information, call 3M: 1-800-328-1667.)

Several remedies are helpful in lessening formaldehyde vapors. Ventilation is perhaps the easiest. Increases in heat and humidity tend to multiply formaldehyde emissions. A constant temperature of 68 degrees F. and 35 percent humidity appears to be ideal.

Asbestos, another extremely hazardous construction pollutant, still exists in many older homes, schools, and commercial buildings. Removal should be done by a contractor professionally trained to handle the offending materials and clean up the residue.

Chemical pollutants. Relatively little is known about the effects of the vast array of chemicals used in households every day - cleaners, paints, glues, pesticides, and personal-grooming products, among them. All contain complex chemicals.

Scientists and industrial experts agree on the need for more research into the indoor environment, where people spend 90 percent of their time.

They also agree that ventilation is the key to solving indoor pollution problems.

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