Robert,

You have much more experience, and expertise, than I. I merely served three years on US boats, and was a TM3. We only had Mk 27's that required charging. Whenever we charged there were signs posted on accesses to the room stating "No Smoking-Charging Batteries". There were fan inserts in the access holes to evacuate the hydrogen.

My opinion---Proper air movement was the key to safely charge batteries--including torpedoes and main batteries.

As an aside: my boat was alongside an English boat in Londonderry. I have to say, that the English were MUCH more casual about charging safety than we were! I came to this conclusion by talking to the crew about their routine procedures.