Running out of compressed air..

[Armistead]

Got myself in a mess after attacking a large invasion force. Escaped, but still fighting a bow dive. Had to blow tanks once. Me and Bubblehead discussed this once, but hard to remember. I didn't take any damage other than forward torp bulkhead, totally flooded. Had to blow tanks once, but slowly I noticed my compressed air going down each hour until the icon displayed. Never blew tanks again, but finally out of compressed air after about 10 hours after blowing tanks..

Course once I got the boat to where it wouldn't sink to the bottom, i'm sure you've all seen the yo yo effect, where you bounce around 30 ft or so.

It appears the game uses compressed air to help control the boat in some way, other than blowing tanks and it's during the yo yo effect. So what is exactly going on here with the compressed air, what's it being used on to run out slowly over time without blowing tanks and no damage to compressor?