Hi tchil01.
If you desire air supply redundancy, in general I do not recommend a Spare Air type unit. The following article from the Dec '00 issue of "Undercurrrent" (
www.undercurrent.org) explains my concerns:
"Is A Spare Air Worth It? How to ensure youre not the next victim."
Cylinders providing extra air for
emergencies come in three basic
forms: A small bailout bottle (like
Spare Air), a pony bottle (a larger
bailout bottle) and independent
twins, which technical divers also use
to provide all the gas they need to
make a dive.
Ponies, which attach to the main
cylinder by various bands, hold
from 6 to 50 cubic feet of air,
although with the higher amount
one might just as well use standard
size independent twins.
Small bailout bottles, like Spare Air, typically
attach to the BC and come in
sizes from a tiny 1.2 cu. ft. to Spare
A i r s 6 cu. ft. 600-Twin, and are
connected to the BC via Ve l c r o
straps, holsters or lanyards. Spare Air
sells three rigs. The least expensive 3
cu. ft. lists for nearly $300 and the
Twin approaches $500 (a sum that
can also buy you a decent pony or
independent doubles set-up and
lots more air). The small Spare Air
cylinder comes with a built-in regulator.
For deeper recreational diving,
and some technical diving, a pony
bottle is the best bet. The question
here is whether there is a value, at
all, to the Spare Air.
For dives above 60 feet, the
largest Spare Air should suffice for
an emergency ascent. Spare Air
advertises 30 surface breaths for the
1.7-cu. ft. unit, 57 for the 3 cu. ft.
and 144 for the Twin 3-cu. ft. set-up.
But, thats on the surface. What
about in an emergency, when one is
down a few atmospheres and
breathing hard? Depending on breathing rate,
to ascend from 60 feet at a brisk 60
feet per minimum without a safety
stop requires anywhere from 2-7 cu.
ft. of air. From 100 feet, its from
about 3 cu. ft. to more than 12 cu. ft.
Given the likelihood that consumption
rates will be greatly elevated in
an emergency out-of-air-situation,
the average diver could expect to
have just enough air to make it quickly
and directly to the surface from
around 60 feet. Surely there is something
to be said for this.
Of course, such an ascent rate
without a safety stop is an open invitation
to DCS. For a slower ascent
and 15-ft. safety stop for three minutes,
youll need proportionately
more air, far more than afforded by
the most generous Spare Air at any
depth. For this reason, it is important
that a diver carrying a Spare Air
not be lulled into a false sense of
s e c u r i t y. Once in trouble, he will
have scant time to solve problems or
even make himself positively buoyant.
Some in the dive community
who have tried a Spare Air, complain
about the lack of it. Leaking
from the regulator is the most frequently
heard disgruntlement. Bob
Parks told Undercurrent that his Spare
Air lost air between dives. While on a
live-aboard last year, the spare air
would lose about one quarter of its
contents over a period of about four
hours. I sent it back to the office in
Huntington Beach, CA and they fixed
the problem, gratis. Don Latta
(Chicago) said his Spare Air would fill
and seemed okay, but the pin gauge
would show half full at the end of the
d a y. Slow leak. Sent unit back; out of
warranty and over $100 to repair it.
Eight months later I checked before a
trip and a faster audible leak this time.
Spare Air fixed it for half price and says
my problem is that I am not storing
with bottle pressurized. After I return
from the trip, I fill the bottle at the dive
shop, however, before my next trip the
bottle is empty again. I fill it at a shop
to check integrity; and air comes out
almost as fast as it is going in. Along
the line, I lost the little screw that acts
as a relief valve on the filler gadget and
d i d n t have time to locate the part; I
bought a second filler for $45. Not a
good experience for a pretty cheap
g u y, but mainly I got to the point were
I just didnt trust the thing. Incidentally,
both dive shops I deal with refuse to
c a r ry the things or be involved in
r e p a i r s .
Because some shops dont want to
deal with Spare Air, this often means
the inconvenience of sending it back
to the manufacturer, with shipping
and handling charges both ways going
on your tab. Dean Michaels, who
works in Florida, says, Ive been repairing
Spare Airs for three years and have
seen hundreds of units that wouldnt
hold air, even after they just got back
from servicing. In all but a few cases it
was a matter of lack of service by the
owner (if it aint broke, dont fix it)
or poor service by someone who
d i d n t have a clue what to do. Most
people seem to think a Spare Air 13.
requires the same amount of service
their tank and valve needs (none).
T h a t s not the case. It is a special use
tool that needs to be checked regularly
and serviced before it is needed
by someone that knows what theyre
d o i n g .
So, if you dont want to tote a
Spare Air, consider one other source
of air for an emergency: your BC.
Air in the BC from the tank con-tains
21% 02 and 16% if orally inflated. Studies
by the YMCA show that
air added to a BC can be rebreathed
13 times or more without becoming
overly hungry for fresh air. While the
technique is not difficult, it does
require some brief instruction and
practice. Interested readers are
directed to the September 1999
issue of Undercurrent for a detailed
description of the technique.
R e m e m b e r, these devices and
techniques are nothing more than
emergency sources, and not ways to
extend dive times. The confidence
provided by carrying an alternate air
source does not absolve the diver from
monitoring his air supply. There is no
reason to run out of air in non-emergencies,
air that is your buddys as well
as yours. -Doc Vikingo"
Hope you found this useful.
DocVikingo
