Almost all experts in dive medicine agree that divers should ascend slowly following dives, whether they’re recreational, working or technical. The reality is that very little direct evidence exists about what ascent rate is safest. Most of the recommendations come from observational studies of bubble grade found using Doppler ultrasound or are based on anecdotal or theoretical concerns.
Sources of contamination include hydrocarbons from compressor lubricants, carbon monoxide (CO) from engine exhaust (or overheated compressor oil) and impurities from the surrounding environment such as methane and carbon dioxide (CO2). Dust particles in breathing gas can also be hazardous, potentially impairing respiratory function or damaging diving equipment. Excessive moisture can cause corrosion in scuba cylinders and other dive gear and may cause regulators to freeze due to adiabatic cooling (heat loss following increased gas volume).
Following training guidelines and conservatively planning our dives can reduce our risk somewhat, but learning how oxygen toxicity affects us and how we can prevent it can mean the difference between a fun dive and one that ends in injury. Push back against complacency and unquestioning acceptance of common practices—understand the effect of oxygen on your body before you plan your next dive.
