DAN Rebreather Study – Caustic Cocktail

DAN researchers are looking for rebreather divers to share their experiences with caustic cocktail(s) while diving and any first aid treatments used subsequently. Currently, there is not much data about how common caustic cocktail events are, who suffers them and how often, if they occur more in highly experienced or less experienced rebreather divers, how long into dives they occur, or how divers respond to them, both immediately and upon surfacing.

If you are a certified rebreather diver and have heard about or experienced a caustic cocktail, we would appreciate if you completed this five-minute DAN Rebreather Survey.

Starts: August 2020


Closed-circuit rebreather (CCR) systems are designed to be waterproof, and bubbles are rarely seen escaping from a functioning rebreather. An exception may be a semiclosed rebreather in which some of the breathing gas is routinely expelled. In fully closed rebreathers, if bubbles are seen escaping then this indicates there is a leak, and water is entering the breathing loop. Such water mixes with the substance packed into the rebreather to absorb carbon dioxide. One outcome of the consequent reaction is the production of highly concentrated caustic soda, which has a pH of 12-14.

Based on interviews with rebreather divers, it is apparent that there exists a range of home remedies for first aid treatment after ingesting caustic soda, popularly known by rebreather divers as a “caustic cocktail”. These home remedies include rinsing the mouth with or drinking a mild acid (such as a carbonated beverage), fruit juice or dairy products.

In fact, the gold standard first aid treatment for ingestion of caustic soda is to immediately flush repeatedly with water, preferably freshwater, but seawater is still effective if freshwater is unavailable. Harm will be minimized if the diver immediately removes the rebreather mouthpiece from their mouth and repeatedly flushes out the mouth with water. Delays can be harmful; one diver described waiting until he had exited the water to gargle with soda, because that is what he was taught during his rebreather diving class. He also reported suffering burns to the inside of his mouth. The sooner the mouth is flushed with water, the less harm will occur from contact with the caustic cocktail. No other treatments are available when the diver is underwater, so flushing with water should commence immediately.

If you have any questions about this study, contact the research team at .