Spare air?

[Mitchell Teeters]

Without getting into all the calculations for that 3 cu ft reserve, think in terms of about a minute - maybe a little more. If my choice were spare air or no air, I know what I would take. But I also know that with a 13 cu ft pony, I can do a normal ascent including a rest stop.

Thanks, I'm still researching this, thanks for info.

 

[RTee]

+1 for considering acquiring a redundant air system based on 40 cft with independent reg assembly vs Spare Air as the first system may be of some use in the future should you choose to take more advanced diving courses

 

[DevonDiver]

Approximately how long will a spare air last for diver that is none stressed?

Visit this resources page - the 'Spare Air Calculator' link is 7th down under 'Basic Scuba'..

Scuba Resources | Diving Articles | Links and Blog | Scuba Tech Philippines



I don't use a spare air, because I don't feel it supplies sufficient gas at the depths I would need it. I'd opt for a more substantial redundant gas supply. In shallower depths, where it can provide some time, I am near enough to the surface to easily conduct an emergency ascent.

I base any emergency scenario gas consumption upon having an elevated/stressed breathing rate. I also factor in a delay in leaving the bottom, as there are decisions to be made, buddies to be looked for and a few seconds for the reality of the situation to sink in. Emergency contingencies have to be calculated upon the worst case scenario. Basing them upon the best case scenario is liable to bite you in the ass.... and that's just what Spare Air do.

 

[irishsquid]

Good points. Approximately how long will a spare air last for diver that is none stressed? ...

If the "Spare Air" is being considered for a redundant/emergency air supply, "stressed" seems to be more a important consideration, though; I guess it would be easier to determine how long it would last under normal conditions and then use a stress factor to multiply by.

I use a slung AL 40 for redundancy. It will get me to the surface from depth safely & with at least some semblence of a safety stop.

+1 for considering acquiring a redundant air system based on 40 cft with independent reg assembly vs Spare Air as the first sytem may be of some use in the future should you choose to take more advanced diving courses

Ditto! I found the 40 to be easy to manage and use it on most of my dives, if for nothing more than practice. Slinging it before getting in the water has become as easy and unobtrusive as wearing a seatbelt, almost a habit.

 

[krawlings]

I sling a AL30 pony on all my deep dives there is ample air for me to safly asend and do a 3min. safty stop.And still have air to spare for the cost I would go the pony rout

 

[Sheri SGR]

here is an article on redundant air sources, number of breaths on three different sized bottles from a specific depth, non stressed diver.

SGR SPECIAL REPORT: Redundant Air Systems

 

[doctormike]

I know that these discussions are fun. However, this particular question comes up very frequently, and it always results the same long series of points, counterpoints, gas calculations, etc...

So if the OP or anyone else is really interested in the community's feelings on the Spare Air, they might as well just read one of the last few threads:

http://www.scubaboard.com/forums/basic-scuba-discussions/400301-spare-air-not.html

http://www.scubaboard.com/forums/basic-scuba-discussions/362674-spare-air-sorry.html

http://www.scubaboard.com/forums/basic-scuba-discussions/355716-pony-spare-air.html

http://www.scubaboard.com/forums/tanks-valves-bands/341044-spare-air.html

http://www.scubaboard.com/forums/basic-scuba-discussions/320812-spare-air-some-thoughts.html

 

[TSandM]

Before buying any piece of equipment, I think it's really important to define the problem that you are solving with it, so you can understand what the value of the equipment is, and what its drawbacks are.

In this case, the problem you are solving is being underwater with nothing to breathe. So let's look at the solutions you have available to you:

1) Don't go there. The vast majority of low on gas or out of gas scenarios are due to diver error: things like failing to check your tank pressure before getting in the water, failing to check your pressure DURING the dive, taking an inadequate gas supply for the proposed dive, and allowing outside (eg. dive guide) pressure to keep you in the water longer than you know is wise. Read the A&I and Near Misses forums and you'll find VERY few incidences of catastrophic gas loss or cutoff of gas supply. It CAN happen (especially in ice diving with freeflows) but it isn't common. When you are diving in conditions where freeflows are common, a better equipment solution is to make sure you have environmentally sealed regulators that are appropriate for the situation, and also learn the appropriate techniques for minimizing freeflow risk.

2) Have a competent buddy close at hand. If you go head down to look at a fish and clog your dip tube, it's likely that the biggest reserve gas supply you have handy is on your buddy's back. This does require some training and discipline, but it really isn't hard to do.

3) Provide yourself with redundancy. This can be in the form of a pony bottle, Spare Air, or double tanks . . . but the one thing it has to be is ENOUGH. Read NW Grateful Diver's article on gas management, because it will give you some mathematical tools to calculate what you may need for self-rescue from a variety of depths. It's more than you think, even if you use a rapid ascent rate and don't make any stops. The one thing you want from emergency equipment is that it be easy to use and reliable -- the one thing I wouldn't want while doing an emergency ascent when out of gas is to run out a SECOND time.

On a much more pragmatic level, a 30 or 40 cf bottle with a standard regulator has much more resale value than a Spare Air, too.

 

[Mitchell Teeters]

here is an article on redundant air sources, number of breaths on three different sized bottles from a specific depth, non stressed diver.

SGR SPECIAL REPORT: Redundant Air Systems

Thanks sheri!

 

[Mitchell Teeters]

There is lots of good info on the links. Thanks. I think that the idea of a RAS is good, how to execute it. It only makes sense to do this, sort of like a reserve parachute. This is an inherently dangerous sport, it just makes sense.