Of almost ( I said ALMOST! ) all full face masks, the Neptune space masks have the lowest
volume, and are very easy breathing ( as long as you follow the instructions! ). That said
I wound that my air usage is lower due to the fact I am far more comfortable diving with a FFM.
Less stress = lower gas consumption.
BUT!
[FLAME SUIT ON] FFM's use more gas than regular in-mouth regulators. PERIOD. [Flame suit off]
How much? Thats probably different for each person. I doubt that I loose more than a couple minutes. BUT I have never really paid that much attention to it. I enjoy my dives more using a FFM. So to me there is no difference. more fun with FFM, or less fun/more jaw ache for a couple min longer? Its a NO BRAINER for me.
I love my OR Neptune Space & OR 1st stage. you can have mine only if you pry it from hands at gun point.
Ive dove KM EXO-26's ( like em, but heavy & the top strap mount hits m in center of forehead & hurts ), AGA's ( Nice, but not as sexy as my OR Neptune space )
Ty