manual inflation of BCD

[Rhone Man]

a 20kg bcd full at 40 m(unlikely) will have 100lts of gas in it.

sac rate 20lts/min is 100lts a min on the bottom.

so thats 1 min of gas on the bottom and about 2 mins at 15m.

Just to round out the calculation - it must be pretty rare anyone gets their BC more than half full, so realistically you are talking about cropping about 30 seconds off your dive time.

I also manually inflate my BC, but to be honest that is just an old habit. I don't expect that it materially extends my dive time.

 

[Necklinsberg]

Regardless of the math, I believe that manually inflating has a psychological effect of making you think about your air consumption.

 

[dumpsterDiver]

I learned to dive with a manual inflation of the BC. Theoretically it does save a tiny bit of air. However, I strongly beleive that a power inflator makes the diver safer.. they can add a bunch of air in an emergency and do it fast. But more importantly, it take two hands to manually inflate,, one to hold the inflator and most people hold the second stage in the other... well I guesss I will hold the anchor line I am descending with my prehensile **** then? or the camera and or light or speargun..... manually inflating the BC is a pain if you are doing anything while diving.

I guess if your hands are free and you don't mind the distraction and the task loading and the activity doesn't bother you, then MAYBE it is worth the theoretical effort to do it manually. Also, unless you are doing a a lot of multi-level diving... You add air on descent and vent air here and there during the dive to compensate for air consumption weight loss.. but with a square profil.. you should not be adding much air in the BC..

I think it is wonderful to practice oral inflation and I would not hesitate to do most dives without a power inflator if something broke... but the device makes the diver safer, and able to be more attentive to their surroundings in my opinion.. defintely worth it.

 

[boulderjohn]

When I see new divers inflating thei bcds off the tank willy nilly, then dumping, then filling some more... I start thinking how much more conservative they might be if they were manually inflating. THEN, I think you might start seeing real conservation of gas!

These divers are either overweighted (as James said), have not been taught to use their lungs properly, or (most likely) both.

You really shouldn't be doing a whole lot of inflating/deflating during a dive. I used to orally inflate, but I don't bother any more. I always carry more gas than I need for a dive, so that extra minute (if that) makes no difference. If you are barely carrying enough to get through the dive, it might be worth considering.

 

[PfcAJ]

on a scale of "1-it doesn't matter"...it doesn't matter. Its more hassle than anything else. When I'm diving, im there to see stuff, not fiddle with gear trying to get an extra 20seconds of dive time.

You'll be better off focusing on getting flat and neutral in the water, diving a properly weighted rig, and reducing dangling junk. Normal dive stuff, if you will.