56
|
SPRING 2014
I
ncidents involving bad breathing gas — be it
air, nitrox, trimix or another mixture — are
rare, yet they do occur. Health effects on divers
vary depending on the contaminant breathed.
Among the most severe symptoms of breathing
contaminated gas are impaired judgment and loss of
consciousness, both of which may be deadly underwater.
Sources of contamination include hydrocarbons
from compressor lubricants, carbon monoxide (CO)
from engine exhaust (or overheated compressor oil)
and impurities from the surrounding environment such
as methane and carbon dioxide (CO
2
). Dust particles
in breathing gas can also be hazardous, potentially
impairing respiratory function or damaging diving
equipment. Excessive moisture can cause corrosion
in scuba cylinders and other dive gear and may cause
regulators to freeze due to adiabatic cooling (heat loss
subsequent to increased gas volume).
Contaminant
Signs and Symptoms
Carbon monoxide (CO)
Headache, dizziness,
weakness, nausea,
vomiting, shortness of
breath, impaired judgment,
confusion, unconsciousness,
potential death
Carbon dioxide (CO
2
)
Hyperventilation, dizziness,
confusion, unconsciousness
Volatile hydrocarbons
Fatigue, headache, confusion,
impaired judgment, numb-
ness, cardiac arrhythmias,
unconsciousness
Oil (condensed)
Headache, nausea, impaired
respiratory function
Dust (particles)
Impaired respiratory
function
Methane
Asphyxia due to dilution
hypoxia
Recommendations for Compressor Operators
Compressor operators can help prevent gas
contamination and mitigate the risk of dive accidents
in several ways.
Attentive compressor maintenance. Proper
compressor maintenance helps ensure breathing-gas
quality as well as extends the life of the compressor.
Breathing-gas contamination is less likely in well-
maintained and properly functioning compressors.
If maintenance is neglected and the compressor
overheats, the lubricating oil may break down and
produce CO and other noxious byproducts.
Effective procedures. A fill checklist can help ensure
safety procedures are remembered when cylinders
are filled. Before starting to fill tanks, the operator
should inspect the compressor’s filters for damage
and note the presence of contaminants such as
cigarette smoke, paint fumes or engine exhaust near
the intake. If the operator notes any chemical or oily
odors after filling has started, he should shut down the
compressor immediately. Other useful strategies for
reducing the risk of gas contamination include keeping
records of air fills and maintenance, ensuring operator
qualifications are up to date, using proper oil and
filters, and maintaining a clean and organized tank-
filling room.
Air-quality testing. As a diver descends and
ambient pressure increases, the amount of gaseous
contaminants breathed also increases. This explains
why a contaminated gas that is not toxic at the
surface may be at depth. Breathing gas must be
tested for a variety of contaminants both regularly
and continuously to ensure compliance with diving-
adjusted contaminant levels.
Compliance with breathing-gas quality standards
is not strictly enforced, and most of the responsibility
for testing lies with the operator. Several methods
of testing are available to compressor operators,
and they vary in price and complexity. Continuous
CO-monitoring devices include electrochemical
sensors with color indicators. Devices that
continuously monitor moisture level are also available.
B y B r i t t a n y T r o u t
RESEARCH, EDUCATION & MEDICINE
//
S A F E T Y 1 0 1
Preventing Breathing-
Gas Contamination
STEPHEN FRINK
