the scrapbook of diving history

How does the Kirby / Yokohama HeO2 Mix Gas Diving Helmet work?

How does the Yokohama HeOs mix gas helmet work?  With ‘Son of a retired Al Krasberg reclaim system builder’ Jim Batgate I took a look at this helmet when he visited me last summer. And with help of ‘Sat Diver’ Marko Hranilovich who provide me with a lot of accurate info on how these helmets were dived I edited this ‘thesis’ (please correct me when I am wrong)

Divers would descend on air to 150 ft to save on expensive helium mixtures so during the first 150 ft of the dive normal air enters through non return valve a. This leads to valve b which regulates the flow of air into the helmet through a silencer/defogger (c) (inside the helmet) At 150 ft they would stop their ascent and the supervisor (at that time called manifold operator) would switch them to Heliox. They would still be on freeflow. They would be instructed to start counting out loud 1, 2, 3, etc, until their voice would change signifying that the umbilical has been flushed free of air and they are on the mixture. Than they would be instructed: 'recirculate, recirculate' and close the freeflow valve b which would direct the gas through valve d to the (first stage SCUBA) reducer e at the back of the helmet. Reducer e is driving the venture nozzle (injector) f (*) recirculating the gas in the helmet/dress. Then the diver tightens the exhaust valve h as far less gas (minimal) would be exhausted. The recirculating of the gas, called the ‘venture’ is done by injector f which shoots the gas past the injector pipe that comes out of the back of the scrubber (g) and there it creates a vacuum which sucks gas from the helmet and passes it through filter g which then re-enters, filtered en enriched with O2, in front side of the helmet where it defogs the faceplate.

On the ascent they would be switched back on air at 150 ft, and go on freeflow again. They didn't know better at the time, and that used to cause quite a few vestibular bends (inner ear decompression illness, due to counterdifussion of nitrogen in the inner ear). They would also follow modified USN tables, first modified/extrapolated by Associated Divers, and leave the 40 ft stop to ascend, be undressed and blown down again to 40ft in the deck chamber all within 5 min, to continue their decompression on oxygen with air breaks to surface.

At first commercial companies would only employ ex USN divers who had Heliox diving experience, later diving schools started training people on those hats, but they were soon outdated by the development of demand valve helmets and masks in conjunction with development of closed bell bounce and saturation diving techniques.

(* unfortunately the hose connecting reducer e and the injector f is missing: do you happen to have a spare one then please contact me at david@divinghelmet.nl. Thanks)


This helmet was last used by the Norwegian navy in 1984 to construct a submarine base at 150 meters of depth, when the job was done the helmet was given as a souvenir to the diver who had used it because it was to be replaced by a more up to date model. Photos David L.Dekker