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THE ORCBS > Occupational Safety > Programs & Guidelines > Confined Space > Confined Space Entry Program >
 Appendix
B. Atmospheric Testing And Monitoring
Procedure For
Atmospheric Testing And Monitoring
Atmospheric
testing is necessary for two purposes: evaluation of the hazards
of the permit space and verification that acceptable entry conditions
for entry into that space exist.
- Evaluation
Testing
The atmosphere
of a confined space should be analyzed using equipment of sufficient
sensitivity and specificity to identify and evaluate any hazardous
atmospheres that may exist or arise, so that appropriate entry
procedures can be developed and acceptable entry conditions
stipulated for that space.
A minimum
of three tests should be performed to identify atmospheric hazards
in confined spaces. These tests must be performed in the following
sequence:
- Oxygen
Content
- Flammability
- Toxicity
- Verification
Testing
The atmosphere
of a permit space which may contain a hazardous atmosphere should
be tested for residues of all contaminants identified by evaluation
testing using permit specified equipment to determine that residual
concentrations at the time of testing and entry are within the
range of acceptable entry conditions.
- Duration
of Testing
Measurement
of values for each atmospheric parameter should be made for
at least the minimum response time of the test instrument specified
by the manufacturer.
- Testing
Stratified Atmospheres
When monitoring
for entries involving a descent into atmospheres that may be
stratified, the atmospheric envelope should be tested a distance
of approximately 4 feet in the direction of travel and to each
side. If a sampling probe is use, the entrant's rate of progress
should be slowed to accommodate the sampling speed and detector
response.
- Equipment
Calibration
To ensure
that the atmospheric testing equipment is functioning properly,
any direct reading test device should not be used without performing
the following three operations:
- Inspection
- Calibration
- Function
Test
All three
operations should be performed according to specific manufacturers
instructions.
AIR MONITORING
GUIDE
- Calibrate
Instrument
- Inspect Instrument
- Check
physical condition of instrument (case, meter, attachments,
hoses for cracks)
- Review
instructions to insure you know how to use the device and
interpret results.
- Perform Function
Test
- Oxygen
sensor: breath into sampling device to reduce the oxygen level
below 19.5%. The oxygen alarm should sound.
- Combustible
gas sensor: remove cap of solvent magic marker or open a cigarette
lighter without a flame near the sampling device until it
reaches a 10% reading. The combustible gas sensor should sound.
- Always
perform a function test in the field before use.
- Never
perform a function test in the suspected atmosphere.
- Pre-Test
Space
- Zero
instrument in known fresh air.
- Test
entire space, top to bottom, every four feet and in the direction
of travel.
- Order
of tests:
- Oxygen
- Flammability
- Toxicity
- Monitor the
Space
- If continuous
monitoring is required, position the instrument near the workers
breathing zone.
If any of
the alarms sound, exit the space immediately.
Always record
your readings.
Contact the
ORCBS if any atmospheric hazards cannot be reduced below the PEL
with ventilation.
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