Oxygen toxicity is a medical condition caused by exposure to oxygen at high pressure. Oxygen toxicity is a concern for scuba divers who dive beyond recreational depth limits, use mixed gasses such as enriched air nitrox, or use gasses with high partial pressures of oxygen for decompression stops. There are two main types of oxygen toxicity: central nervous system (CNS) oxygen toxicity and pulmonary oxygen toxicity.
CNS oxygen toxicity is usually caused by divers exposing themselves to an oxygen partial pressure of 1.6 ata or greater, and can result in convulsions, pulmonary barotrauma, and death.
Pulmonary oxygen toxicity is caused by divers exposing themselves to elevated partial pressures of oxygen for long periods of time, and is primarily a concern for technical divers who decompress on oxygen. Pulmonary oxygen toxicity causes a burning sensation in the trachea, coughing, shortness of breath, and eventually lung failure.