There are several different levels of formaldehyde exposure that must be measured. The Short Term Average Exposure Limit (STEL) is the average maximum exposure allowed in 15 minutes. If your lab is found to exceed the STEL, you will be required to do monitoring at least once per year. If you conduct your initial monitoring and you exceed the Action Level (.5 ppm), further monitoring is required at least every 6 months. You may also see a ceiling value, which is the maximum level that can’t be exceeded at any time. If you see IDLH, that is bad news. IDLH stands for immediately dangerous to life or health. You’re unlikely to see this in the histology lab in connection to formaldehyde, but it is worth noting for general chemical safety.
Your lab can stop its regular monitoring if two consecutive tests come back with exposure levels below the action level and STEL. You should however, do formaldehyde exposure testing whenever there is a change to processes or equipment, as this could impact the levels of exposure. You will also be required to do formaldehyde monitoring if someone reports symptoms of exposure, which include watery eyes, burning of the eyes, nose, throat, coughing, nausea, and skin irritation.
Find out more about chemical safety, in NSH's QLS Prep Course.