When a diving accident occurs, being able to recognize the problem and respond with the appropriate care can speed the diver’s recovery and minimize lasting effects. Oxygen first aid provides needed oxygen to body tissues, enhances the elimination of inert gases such as nitrogen obtained from breathing gases, and helps shrink any gas bubbles that may have developed during ascent — bubbles that contribute to decompression sickness and arterial gas embolism. Supplemental oxygen also can help minimize or eliminate existing symptoms and reduce further injury until medical services are engaged.