Chlorine inhalation may rapidly cause pulmonary edema, leading to acute hypoxemic respiratory failure. We report a 12 year old with acute respiratory failure from inhalation injury after he accidentally dropped chlorine tablets into a swimming pool. Supplemental oxygen alone failed to provide adequate arterial oxygenation. We administered positive end expiratory pressure (PEEP) in the emergency department, resulting in markedly improved oxygenation. Early institution of PEEP should be considered in patients with chlorine poisoning when supplemental oxygen alone is insufficient.