A 67-year-old woman with morbid obesity and severe obstructive sleep apnea presented to the emergency department with 2 days of productive cough, fever, shortness of breath and loose stools. A chest x-ray showed extensive bilateral infiltrates, and she was quickly intubated for acute hypoxic respiratory failure. A urine legionella antigen test was positive, and she was admitted to the intensive care unit with a diagnosis of severe legionella pneumonia. She improved over the next week with a course of levofloxacin. Once improved, the state health department visited her home and interviewed her husband and determined that she had not been cleaning her continuous positive pressure mask, tubing and humidifier appropriately. They concluded that the legionella likely came from her continuous positive airway pressure equipment. Cases of legionella pneumonia have frequently been reported through infected water supplies and even respiratory equipment. It is crucial that the mask and tubing used with these devices are cleaned appropriately to minimize the risk of infection.