Mass exposure to chloramine gas has not been reported. We report two groups of 36 patients (72 total) suffering from acute inhalation of chloramine gas. Chloramine gas is produced from mixing common household cleaning agents containing sodium hypochlorite (bleach) and ammonia. The first mass casualty event occurred when 36 male soldiers were exposed during a "cleaning party" in their barracks. Ten days later, 36 female soldiers were exposed in a similar manner and presented to our emergency department. In each event, commonly available cleaning agents--liquid bleach and ammonia--were mixed together, liberating toxic chloramine gas. Nebulized sodium bicarbonate solution has been suggested for treatment of chlorine gas inhalation, but no report of nebulized sodium bicarbonate for treatment of chloramine gas inhalation injury exists. In our series, 22 patients exposed to chloramine gas were treated with a nebulized solution of 3.75% sodium bicarbonate. This treatment made no significant statistical or clinical difference in outcome. We present the largest case series of patients presenting to an emergency department for treatment of acute inhalation of chloramine gas.