Nitrous oxide levels in the emergency department.

Levels of nitrous oxide were monitored in the emergency department during the use of a Nitronox machine after four and eight minutes of breathing gas. Levels near the user's head were found to be 800 to 1,200 parts per million. Levels at the center of the room peaked at 300 ppm after eight minutes of use, and spot checks in the emergency department hall adjacent to the test room were less than 10 ppm. Ventilation was measured in the test room and was found to influence the peak level of nitrous oxide and the rapidity of washout of the gas from the room. The results of this study should prompt the development of guidelines for the use of nitrous oxide in the emergency department setting.