Cooling systems in rebreathers
Cooling breathing gas in the loop
For applications requiring entering a room with high temperatures or breathing for long periods from a closed system, the temperature in the breathing circuit can become higher. For this reason, since 1930 some breathing apparatus has been equipped with an integrated cooler. A distinction is made between cooling by means of ice and chemical cooling. Systems have been developed for this in England and Germany. You can read more about these on this page.
The English Proto rebreather is used by fire brigades, miners and for underwater applications.
The copper part looks like the scrubber but it is not! It is the Cooler! The cooler is a flat oval copper container having the filler on the side. The cooler has two connections, a female for connecting to the breathing bag /canister and a male at the top for connecting to the breathing tube. To ensure that the oxygen passes round the inner container a baffle plate is fitted in the outer container. (see picture below). Into the inner container is poured the cooling agent, approximately 10 oz. (284 grams)of calcium chloride (hexahydrate)(antarcticite note author). In crystallized form at normal temperatures, calcium chloride has the property of absorbing large amounts of heat before beginning to liquefy at about 86 degrees Fahrenheit ( 30 degrees Celsius). This container with its filling cap is placed inside and is integral with the outer container which has the two mentioned connections. The latter is on a swan neck and connects to the breathing bag, whilst the inhaling tube is attached to the male connection of the cooler. After use, cold water must be circulated around the outer container to revert the calcium chloride to its crystallized form. Under no circumstances should the cooler be polished since a polished surface attracts exterior heat and this effect will obviously reduce the efficiency of the cooler! The latest cooling agent to be used is sodium phosphate which begins to liquefy at 97 degrees Fahrenheit!
Antarcticite is an uncommon calcium chloride hexahydrate mineral with formula: CaCl2·6H2O.
It forms colorless acicular trigonal crystals. It is hygroscopic and has a low specific gravity of 1.715.
Therebreathersite was founded by Jan Willem Bech in 1999. After a diving career of many years, he decided to start technical diving in 1999. He immediately noticed that at that time there was almost no website that contained the history of closed breathing systems. The start for the website led to a huge collection that offered about 1,300 pages of information until 2019. In 2019, a fresh start was made with the website now freely available online for everyone. Therebreathersite is a source of information for divers, researchers, technicians and students. I hope you enjoy browsing the content!