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• A nitrox stick mixes oxygen with air in the intake

of the high-pressure compressor. This method also

warrants caution since pure oxygen must be used.

The oxygen is metered into the stick so that the end

product produced is the targeted percentage.

• A membrane system moves low-pressure air through a

membrane that pulls away nitrogen so that a mix that is

higher in oxygen remains. This desired gas is delivered

to the intake of the high-pressure compressor.

Regardless of the means of nitrox production, the

creation of nitrox is best left to diving professionals

for safety considerations. A nitrox course provides the

information necessary for understanding what mix to

use for diving at various depths.

To help ensure their air is safe, recreational divers

can do the following:

• Prior to using a compressed-air cylinder, carefully

open the valve slightly and check for any odors. If an

odor is present, do not use the cylinder. An odor may

indicate that the filtration system on the compressor

that purified the air is either past due

for servicing, has had a mechanical

failure, has drawn in harmful vapors or

has been contaminated by an autodrain

system failure.

• If the cylinder is filled with nitrox, analyze the

oxygen percentage prior to use to ensure that it

is as expected. Cylinders containing gases other

than air by law must be marked with the gas

they contain.

• Consider using a CO sensor or analyzer. CO-Pro

by Lawrence Factor, for example, is a quick,

effective and affordable way to check for the

presence of CO.

• Most important, find a high-pressure air source

you can trust. Some states (such as Florida) require

quarterly air testing. Ask the facility where you buy

your air what preventative maintenance practices

they follow. Most dive operations are proud of their

air and nitrox systems and would be happy to show

them off.

Compressing breathing air or nitrox into a scuba

cylinder is hard work — for both the compressor and

the technician operating the equipment. Vigilance and

regular maintenance are required to ensure that the air

produced is certifiable to the Compressed

Gas Association’s Grade E standards

for scuba. Play it safe by knowing your

source so you can feel confident about

the gases invading your body tissues.

ALERTDIVER.COM

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For more tips and incident

reports, or to report a diving

incident, visit

DAN.org/

diving-incidents

Divers can help ensure the

quality of their breathing gas by

smelling it, analyzing it, testing

it for CO and, perhaps most

important, getting it from a

reputable, trustworthy source.

STEPHEN FRINK