THINK DETAILS FOR AIR TOXICITY

                   Is the concentration > MAC or TLV_TWA?

The so-called “do-nothing” action in reality means a great deal and involves monitoring the situation as it evolves during the incident.

As a rule of thumb, over a short exposure there should be no effect if the concentration is less than the maximum allowable concentration (MAC) or less than the threshold limit time-weighted average (TLV_TWA).  These are workplace concentration values used as a guide for the maximum safe exposure to a chemical for a normal 8-hour working day and 40-hour working week.