Is Your Drywall Making You Sick?

Jonathan I. Katz

Professor of Physics

Washington University

St. Louis, Mo. 63130

[my last name]

It has been widely reported that some recently installed drywall of Chinese origin has produced corrosion of metals and illness of occupants in houses in which it is found. A plausible explanation is that this drywall emits hydrogen sulfide. This gas is very toxic, and after brief exposure the nose becomes insensitive (as long as the exposure continues) to its noxious smell. It also reacts with iron to make black iron sulfide, whose appearance resembles that of the observed corrosion.

The principal component of drywall is calcium sulfate. If this is contaminated with calcium sulfide and the chemistry is acid (either from the calcium sulfate or some other acidic contaminant) hydrogen sulfide gas will be evolved.

A possible means of mitigating this problem may be to paint the drywall with lime water or lime wash (calcium hydroxide solution). This should soak into the drywall deeply enough to neutralize the excess acidity. Alternatively, a washing soda (sodium carbonate) solution might be used.

These chemicals are very cheap and widely available. Their alkalinity makes them irritating to the skin, but they are generally safe to handle and use. However, eye contact should be avoided.

If the house has forced air ventilation with a humidifier, one of these alkali solutions should be used in the humidifier in place of pure water, and the system run continuously. This would remove hydrogen sulfide from the air. Calcium sulfide (or sodium sulfide, if washing soda is used) would precipitate as a sludge in the humidifier, which must be cleaned regularly, and the alkali replenished.

Jonathan Katz
Friday September 11 2009