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Operators can send a breathing-gas sample to an
accredited laboratory for analysis of oxygen, CO,
CO
2
, moisture, oil/hydrocarbons and even particulate
matter; this is recommended on a quarterly basis.
Air Quality Specifications for Recreational Diving
Contaminant
Maximum Levels
Oxygen
20-22%
Carbon dioxide
1000 ppm
v
Carbon monoxide
10 ppm
v
Total hydrocarbons,
including methane
25 ppm
v
Oil/particles
5mg/m
3
Water vapor
67 ppm
v
Objectionable odors
No odor
Source: Compressed Gas Association (CGA) Grade E, National
Fire Protection Association (NFPA) 1500, American National
Standards Institute (ANSI/CGA G-7.1’97)
Recommendations for Divers
Ask questions and be observant. If you are unsure
about the breathing-gas quality at a fill station, ask
questions about compressor maintenance, procedures
and testing. Ask if the compressor operator monitors
for CO and how often they send samples to a lab
for analysis. Look for posted breathing-gas-analysis
reports, and note whether the fill room is clean,
organized and well ventilated. Observe the proximity
of the compressor intake to sources of exhaust, and
look to see whether the compressor has an hour meter
that can be monitored for regular maintenance.
Always conduct a predive gas check. If your breathing
gas has an unusual odor or taste, do not dive with it —
this is a red flag for oil or combustion contamination.
However, keep in mind that not all contaminants can
be detected this way; CO, for example, is odorless and
tasteless. Electronic CO detectors or products such as
CO-PRO
TM
can be used to detect the presence of CO in
breathing gas. Divers should always use oxygen analyzers
to determine the level of oxygen in a nitrox mixture to
prevent oxygen toxicity.
Confirming Contamination
Identifying contamination incidents based on
symptoms alone is difficult, as the associated
symptoms are often similar to other diving-related
and nondiving illnesses. If a diver suspects he was
exposed to bad breathing gas, he should seek a medical
evaluation and have the gas tested. Observing the
health of other divers who had their tanks filled at the
same source may be helpful in determining whether a
diver’s symptoms are related to contamination.
DAN Research
DAN occasionally receives reports of problems from
divers breathing contaminated gas, but we suspect
this issue is underreported. To encourage divers to
report compressed-gas contamination, DAN will assist
with gas analysis. If you were involved in an incident
possibly related to breathing contaminated gas and
you have lawful control of the tank, please preserve the
tank and contact DAN Research at 919-684-2948 or at
AD
References
Burman F. Scuba air quality. Alert Diver Southern
Africa. Autumn 2013: 14-18.
Millar IL, Moudley PG. Compressed breathing air: the
potential for evil from within. Diving and Hyperbaric
Medicine. 2008; 38: 145-51.
From far left: A neat and clean filling room promotes
adherence to quality control. CO is tasteless and
odorless; detection requires testing. Test kits and
paperwork for sampling and sending off breathing
gas quarterly
STEPHEN FRINK
BRITTANY TROUT
COURTESY DOWN UNDER SURF AND SCUBA
