Sampling Procedure
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.
Atmospheric Monitoring
- Electronic gas detectors and color-indicator gas detector tubes are the most common types of instruments used for determining oxygen content, lower explosive limit, and toxic atmospheres.
- Evaluation and interpretation of this data and development of the entry procedure should be done by or reviewed by, a technically qualified person based on evaluation of all serious hazards.
- The atmosphere should be tested for residues of all contaminants identified by evaluation testing to determine that residual concentrations at the time of testing and entry are within the range of acceptable entry conditions.
When monitoring for entries involving a descent into atmospheres that may be stratified, the atmospheric envelope should be tested about every 4 feet (1.22 m) in the direction of vertical travel and to each side. If a sampling probe is used, the entrant's rate of progress should be slowed to accommodate the sampling speed and detector response.
- Results of testing should be recorded on the permit in the space provided adjacent to the stipulated acceptable entry condition.
- If entrants leave the confined space for any reason, they should once again test the atmosphere before re-entry into the confined space because it can change rapidly.
- Test results that show the composition of an atmosphere to which employees are exposed (even if the employees are using respirators) must be available to members of the entry team or representatives.
Knowledge Check Choose the best answer for the question.
2-10. The confined space atmosphere during entry should be tested about every _____ in the direction of vertical travel and to each side.
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