The following tests should be done on a sample of air obtained
from the compressor after it has been in operation for at least ten minutes
thereby permitting observation of the effects of heating the motor.
Oxygen: 20-21 percent.
Compressed ambient air will be considered to meet the oxygen standard without
testing. If such tests are required, a sample blown into a plastic bag, such as
polyvinyl chloride (pvc) film or aluminized Scotchpak or flushed through an
all-glass evacuated flask, may be analyzed with an oxygen indicator such as the
Portable Oxygen Indicator of the Portable Gas Analyzer.
Carbon dioxide: Less than.03
percent (300 ppm). Compressed ambient air will be considered to meet the
carbon dioxide standard without testing. If such tests are required, a sample
blown into a plastic bag, such as pvc or aluminized Scotchpak or flushed
through an all-glass evacuated flask, may be analyzed with a gas analysis
apparatus or with gas detector tubes such as the Kitagowa Gas
monoxide: Less than .001 percent (10 ppm). Carbon monoxide may be
analyzed by first collecting an air sample directly from the compressed gas
tank or compressor into a plastic bag, such as pvc or aluminized Scotchpak, or
into an all-glass evacuated flask. The collected sample may be analyzed by
means of direct reading indicating tubes or by means of a direct reading CO
Indicator, or by means of the laboratory techniques with iodine pentoxide or
Oil mist: Less than 5
Oil mist may
be analyzed by first collecting an air sample on oil-free silica gel or on a
molecular filter sampler. Since oil droplets tend to settle on the walls of any
holding container, the air sample should be passed directly from the air
compressor or air tank to the silica gel or molecular filter sampler.
When the sample is collected on silica gel, the oil may be
analyzed by extraction with a known volume of carbon tetrachloride and compared
for fluorescence under a "dark lamp", using known quantities of S.A.E. No. 30
petroleum lubricating oil in carbon tetrachloride for standards.
An alternate method may be used, by collecting a known volume
of air on a molecular filter sampler and comparing the "black light"
fluorescence with known standard quantities of S.A.E. No. 30 oil. For example,
with the "RV Black Light", a 30 microgram quantity of lubricating oil can be
detected on a 47 mm molecular filter paper. Thus a 6 liter air sample, through
a molecular filter, will detect a concentration of 5
mg/M3 of oil mist. Repeated samples, at higher or
lower total air volume, can be collected to estimate the magnitude of oil mist
Mineral or silicone oil which occasionally are used for
compressor lubrication do not fluoresce under ultraviolet light. Where these
oils are used assay should be done by gravimetric analysis at a micro-chemical
oxidants: Less than 0.05 ppm.
Total oxidants in compressed air may be
analyzed by two methods:
(1) A 20 liter air
sample may be collected directly from the tank or compressor into an all-glass
midget impinger of fritted glass absorber sampler, containing 10 ml of
(2) A 20
liter sample may be collected in a Mylar plastic bag and returned to a
microchemical testing laboratory for analysis by the phenolphthalein reagent
method. Since total oxidants in air are not chemically stable, their analysis
should be undertaken within a few hours of collection.
Total hydrocarbons: Less than 50
Total hydrocarbons may be analyzed by two methods:
(1) A sample of compressor or tank air may be
collected into a plastic bag, such as aluminized Scotchpak or Mylar, and
returned to the laboratory for analysis by gas chromatography.
(2) The magnitude of the total hydrocarbon
concentration may be estimated, semi-quantitatively, by means of combustible
gas indicator. Most combustible gas indicators indicate a concentration of
approximately 50 ppm with a 5 percent of full-scale deflection for most
Odor: None detectable. No quantitative tests have been
standardized for odor measurement. Therefore, any odor, detectable by olfactory
sensation, will be considered unacceptable. Yaglou and Borum have classified
odor sensations as: (1) neutral, (2) perceptible, (3) moderate or acceptable,
(4) strong, (5) very strong, and (6) over-powering or nauseating. Any
classification above (1), will be considered unacceptable for SCUBA
Water vapor: No
quantitative test for water vapor is recommended. Compressed air, at
3,000 psi, saturated with water vapor, contains less than 1 grain of water per
pound of bone-dry air. When this air expands to normal atmospheric pressure, or
even two or three atmospheres of pressure, the relative humidity is less than