Basic HTML Version
Chapter 24 — 2
Fig. 24.1
Schematic diagram of a compressor system with filters.
GAS PURITY STANDARDS
Authorities such as the US Navy, NOAA and Standards Australia specify minimum standards
of purity for breathing gas.
Case History 24.1
In an area subject to tidal currents an experienced diver planned to dive at slack water.
He anchored his boat almost at low tide. The hookah compressor he used was correctly arranged with the air
inlet upwind of the exhaust and the dive commenced. After 90 minutes at 10 metres the diver felt dizzy and lost
consciousness but was fortunately pulled aboard by his attendant and resuscitated.
Diagnosis
— Carbon monoxide poisoning
.
Explanation — as the tide turned, so did the boat. This put the compressor
air inlet
downwind of the motor
exhaust
and carbon monoxide from the exhaust was breathed under pressure by the diver.
Compressors can also generate some lethal contaminants internally. The compressor piston
requires lubrication and this is usually achieved by the use of special
oils
. In some
circumstances, such as where there is excessive wear of the compressor, high temperatures
can be generated and this may decompose the lubricating oil into toxic products such as
oxides of nitrogen
or
carbon monoxide
, which are then pumped into the diver's air tank.
Poor maintenance of the compressor can also lead to an
oil
and
hydrocarbon
mist escaping
into the air supply.