What Every Diver Should Know About Oxygen Toxicity
Oxygen toxicity can be deadly if ignored. Learn how it happens, how to spot the warning signs, and how to stay within safe diving limits.
SAFETY WHILE DIVING
What Every Diver Should Know About Oxygen Toxicity
Oxygen keeps us alive, but underwater, it can turn dangerous. Oxygen toxicity happens when a diver breathes high concentrations of oxygen at depth — and it can lead to seizures, loss of consciousness, and even death if not properly understood. While most recreational divers are unlikely to experience it if following standard dive tables and using air or nitrox correctly, awareness of this condition is still vital.
There are two types of oxygen toxicity: central nervous system (CNS) toxicity and pulmonary toxicity. CNS toxicity is the one divers worry about most because it can strike suddenly and without warning. Symptoms include visual disturbances (like tunnel vision), ringing in the ears, nausea, twitching, dizziness, and convulsions. Pulmonary toxicity develops from prolonged exposure to elevated oxygen levels and is more relevant on extended technical dives, usually over several hours or repeated exposures.
The risk increases with depth because pressure affects how much oxygen dissolves in your body. The key number to remember is 1.4 ATA (atmospheres absolute) — that’s the maximum partial pressure of oxygen recommended for recreational diving. This number is especially important when diving with nitrox (enriched air), which contains more oxygen than regular air. For instance, a diver using 32% nitrox reaches 1.4 ATA at about 111 feet. Going deeper increases the risk significantly.
To prevent oxygen toxicity:
Always analyze your nitrox mix and set your dive computer accordingly
Stick to your maximum operating depth (MOD) for the blend
Plan dives carefully, especially when using higher oxygen percentages
Avoid rapid ascents or poor buoyancy control, which could increase exposure
Stay well within limits — don’t “ride the edge” of your MOD
This is where training comes in. Nitrox certification courses cover oxygen toxicity in detail and teach you how to manage exposure safely. If you plan to explore deeper or longer dives, especially with mixes richer in oxygen, getting trained in technical diving is crucial.
While oxygen toxicity is rare in recreational diving, it’s not unheard of. Many incidents involve a mix of poor planning, improper gas analysis, or divers pushing limits. Respecting the physics and physiology of diving isn’t about fear — it’s about informed confidence.
Stay educated, stay alert, and your dives will stay enjoyable. Knowing about oxygen toxicity isn’t just for tech divers — it’s something every diver should have in their mental toolkit.
Happy and safe diving,
The ScubaBlast Team
Divers Alert Network. (2024). Oxygen Toxicity. https://dan.org/health-medicine/health-resources/dive-conditions/oxygen-toxicity/
PADI. (n.d.). Understanding Oxygen Toxicity in Diving. https://www.padi.com/education/oxygen-toxicity
National Oceanic and Atmospheric Administration (NOAA). (2019). NOAA Diving Manual (5th ed.). https://www.omao.noaa.gov/find/media/documents/noaa-diving-manual-5th-edition
Scuba Diving Magazine. (2022). The Truth About Oxygen Toxicity. https://www.scubadiving.com/oxygen-toxicity-dive-safety