The head dome: a simplified method for human exposures to inhaled air pollutants.

Acute controlled exposures of human subjects to air pollutants are customarily carried out with whole-body chambers, masks, or mouthpieces. The use of these methods may be limited by cost or technical considerations. To permit a study involving a highly unstable pollutant, artificial acid fog, administered to subjects during natural breathing, a head-only exposure chamber, called a head dome, was developed. It consists of a transparent cylinder with a neck seal which fits over the subject's head and rests lightly on his shoulders. The head dome does not constrain the upper airways or impede exercise on a bicycle ergometer. Ventilation can be monitored accurately and unobtrusively with a pneumotachograph at the exhaust port of the dome. A thermocouple may be used to monitor the onset and persistence of oronasal breathing. For short-term exposures to unstable or reactive pollutants lasting up to several hours, the head dome is an effective alternative to a whole-body chamber and probably superior to a face mask or mouthpiece.