Nitrous oxide contamination in dental surgeries using relative analgesia.

The concentrations of nitrous oxide were determined at various positions in four dental surgeries in which nitrous oxide sedation was used without scavenging. Contamination was present in all the surgeries, the greatest concentration being recorded at the dentist's nose and the least in the peripheral air. The reception area adjoining the surgeries was found also to be contaminated by nitrous oxide.