664 HAZWOPER for General Site Workers V

Factors for Consideration

Several factors should be considered when using total atmospheric vapor/gas concentrations as a guide for monitoring a selected Level of Protection.

• The uses, limitations, and operating characteristics of the monitoring instruments must be recognized and understood. Instruments such as the photoionization detector (PID), flame ionization detector (FID), and others do not respond identically to the same concentration of a substance, nor do they respond to all substances.
• Other hazards may exist such as gases not detected by the PID or FID, explosives, flammable materials, oxygen deficiency, liquid/solid particles, and liquid or solid chemicals.
• Vapors and gases with a very low Threshold Limit Value (TLV) or IDLH value could also be present. Total readings on instruments not calibrated to these substances may not indicate unsafe conditions.

The risk to personnel entering an area must be weighed against the need for entering. Although this assessment is largely a value judgment, it requires a conscientious balancing of the known and potential risks to personnel against the need to enter an unknown environment.

The knowledge that suspected carcinogens or extremely toxic substances are present requires an evaluation of several factors, such as:

Based upon total atmospheric vapor concentrations, Level C protection may be judged adequate; however, tasks such as moving drums, opening containers, and bulking of materials, which increase the probability of liquid splashes or generation of vapors, gases, or particulates, will likely require a higher level of protection.

The following module section pages provide more information on levels of protection.

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