Using Vapor/Gas Concentrations to Determine Level of Protection
The objective of using total atmospheric vapor/gas concentrations is to determine a numerical criterion for selecting the appropriate level of PPE (e.g., Level A, B, or C).
In situations where the presence of vapors or gases is not known, or if present, the individual components are unknown, personnel required to enter that environment must be protected.
Total vapor/gas concentration can be used as a guide for selecting PPE until more definitive criteria can be determined (e.g., until the constituents and atmospheric concentrations of vapor, gas, or particulates can be determined, and until respiratory and body protection can be chosen that relate to the toxicological properties of these constituents).
Although total vapor/gas concentration measurements are useful to a qualified professional for the selection of protective equipment, caution should be exercised in their interpretation because:
- An instrument does not respond with the same sensitivity to several vapor/gas contaminants as it does to a single contaminant.
- Total vapor/gas field instruments detect all contaminants in relation to a specific calibration gas, therefore, the concentration of unknown gases or vapors may be either overestimated or underestimated.
- Suspected carcinogens, particulates, highly hazardous substances, infectious wastes, or other substances that do not elicit an instrument response may be known or suspected to be present.
For the reasons stated above, the protection level should not be based solely on the total vapor/gas criterion. Rather, the level should be selected on a case-by-case basis, with special emphasis on potential exposure from the chemical and toxicological characteristics of the known or suspected material.
Knowledge Check Choose the best answer for the question.
5-6. When selecting PPE, the protection level should be selected _____.
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