Common industrial chemicals are often monitored for combustion (as a percentage of the lower explosive limit (% LEL), but should be monitored in ppm to protect personnel to OSHA standards.
For example, monitoring Toluene at 10% LEL results in an alarm setting of 1100 ppm – 11 times the TWA limit of 100 ppm, and over 2 times the IDLH level.
All of the information below is from the NIOSH Pocket Guide to Hazardous Chemicals available at https://www.cdc.gov/niosh/npg/search.html
- 100 LEL % = 1,000,000 ppm
** PPM = LEL % by Vol x % LEL . Example Toluene 1.1% LEL x 100% LEL (1,000,000 PPM) = 11,000 ppm
*** IDLH – immediately dangerous to life or health concentrations
TWA – time weighted average – the average exposure that must not be exceeded during any
8 hour work shift of a 40-hour work week.