Breathing Air ContaminationThe
quality and purity of the air you breathe while scuba diving is an
important safety factor that you may take for granted. We live and dive
in South Florida where we are surrounded by excellent scuba shops that
provide us with high quality diving cylinder refills of both air and
nitrox. This, however, has not always been the case, and may not
be the circumstance you find yourself in if you dive in remote portions
of the world.
What are the most common contaminants in diving
air? How might you detect each contamination, and what are its
Water: When humid air is compressed, water
condenses within the SCUBA compressor. The typical multistage SCUBA
compressor has moisture traps after each stage. If these moisture traps
malfunction, significant water can be discharged from the compressor
along with the airstream. If the entrained water is sufficient, it may
overwhelm the final discharge filter, and allow some water to be pumped
into your SCUBA cylinder. Small amounts of water in a SCUBA cylinder
generally go undetected until the cylinder is visually inspected. If a
large amount of water enters a SCUBA cylinder it may pass through the
cylinder valve into a regulator when the diver is inverted. This may
cause momentary malfunction of the regulator and the diver may get a
mouthful of water with a foul taste.
Compressor oil: The
typical scuba compressor has reciprocating pistons that move within
cylinders, somewhat similar to an internal combustion engine. These
reciprocating pistons are lubricated with oil just as they are within
your automobile engine. However, the oil used in SCUBA compressors is
food grade oil that is safe for human consumption. Some of this
compressor oil is discharged from the compressor along with the output
air. It normally is removed by the final condensate trap and the final
output air filter present on the compressor. However, if the output air
filter malfunctions or is not changed on schedule, oil can pass into
your SCUBA cylinder. Small amounts of oil in a SCUBA cylinder may cause
the air to taste or smell or may go undetected until the cylinder is
visually inspected. If a large amount of oil enters a SCUBA cylinder it
may pass through the cylinder valve into a regulator when the diver is
inverted. This may cause momentary malfunction of the regulator and the
diver may get a mouthful of oil with a foul taste.
Monoxide (CO): Carbon monoxide may pass into an air intake system
for a SCUBA compressor when the air intake is close to the exhaust of
an internal combustion engine. This is most commonly associated
with a SCUBA compressor that is driven by a gasoline or diesel engine.
However, it could also occur if a running automobile, truck or boat
engine exhaust is close to the air intake of the SCUBA compressor
(while your cylinder is being filled). The output air filter of a
modern SCUBA compressor is designed to remove CO but there’s always the
possibility of a malfunction or lack of timely filter replacement.
monoxide contamination in your breathing air is a serious issue.
It may cause headache, dizziness, nausea, vomiting, shortness of
breath, confusion and loss of consciousness.
Takeaway: Have your SCUBA cylinders filled at a reputable SCUBA
shop. If you’re at an unfamiliar shop, ask to see the SCUBA compressor,
and inquire when the output air filter was last replaced. If you
don’t come away with a warm and fuzzy feeling, go somewhere else for
your tank fill.
Be safe, Dive safe
And, may your SCUBA regulator always taste and smell like fresh mountain air!