There is surprisingly little evidence to implicate lack of humidity as a source of sickness. If the relative humidity is less than thirty per cent, dryness of the skin and irritation of the nose and throat may occur. Before you rush out to buy a humidifier, however, try lowering the thermostat a few degrees. The hotter you keep your home, the more moisture you need in the air. Humidifiers are dangerous breeding grounds for mold and bacteria. Anti-foulants added to the water in a humidifier are worthless in controlling bacterial growth and themselves pose a health hazard if inhaled. Medical advice to humidify the air for improving respiratory problems has little evidence to support it. Only humidify your home air if you notice a definite improvement in pre-existing respiratory complaints; otherwise the risks outweigh the benefits. If you must use a humidifier, use a cool mist or ultrasonic room unit that is not connected to your central heating system. It will be much easier to clean. Use only distilled water in the reservoir and drain the unit daily, cleaning it with hydrogen peroxide diluted one-to-one with distilled water.
(4) Check appliances and sources of combustion. Stoves, heaters and dryers that burn fuel of any kind may generate carbon monoxide and nitrogen dioxide. If the appliance is improperly maintained or vented, carbon monoxide poisoning can occur. Acute carbon monoxide exposure can cause death by asphyxiation, heart attacks, headache, lethargy, hyperactivity, irritability, confusion, bizarre behavior, shortness of breath, chest pain, nausea, blackout spells and seizures. Acute poisoning may be followed by evidence of brain damage two to four weeks later. The delayed symptoms include memory loss, unclear speech, visual disturbances, unsteady gait and personality changes. Chronic low grade exposure may cause subtle deterioration in mental function and hearing loss. Sometimes the first signs of carbon monoxide toxicity in the home are morning headache or dizziness and difficulty concentrating. Information on low-cost carbon monoxide detectors is available from the Consumer Products Safety Commission (800-638-2772).
Nitrogen dioxide is a respiratory tract irritant that can cause sore throat or cough and increase the rate at which allergies develop. It has been shown to increase the spread of cancer in experimental animals. Its main indoor sources are appliances that burn natural gas and kerosene space heaters. Nitrogen dioxide emissions in homes are greatly reduced by venting appliances to the outside and by the electrical ignition of gas stoves rather than the use of a pilot light.
(5) Reduce formaldehyde levels. Because of the extensive use of building materials and furnishings which release it, formaldehyde exposure is almost inescapable in modern indoor environments. The greatest levels are given off by the glue which holds together fiberboard, particleboard, and plywood panelling. New houses with particle board sub-flooring and mobile homes are loaded with formaldehyde. Although formaldehyde emission eases with time, high humidity or moisture disintegrates the glue and increases formaldehyde release. Formaldehyde is used to stiffen fabrics of all types, so that new clothing, carpeting and upholstered furniture may off-gas considerable formaldehyde for days or weeks. Other sources of formaldehyde in household air are foam insulation, urea-formaldehyde finish coatings on furniture and flooring, fresh latex paint, space heaters, new paper or plastic products of any type, and cosmetics (including nail polish, skin creams, and hair sprays).