There is a lot of talk about a process being “PSM Covered” however, how is that defined? There are two different definitions outlining whether a chemical and therefore the attached process is PSM Covered. The first, and more generally referred to definition, is for quantities over 10,000 lbs. of flammable chemicals (defined as having a flashpoint below 100 Deg F). The second definition is a little more obtuse. There is a list of 77 Highly Hazardous Chemicals with threshold quantities published by OSHA. What is a Highly Hazardous Chemical and who has ever taken the time to research the list of them along with the threshold quantities to see what they really are? OSHA’s PSM standard defines a Highly Hazardous Chemical to mean: “a substance possessing toxic, reactive, flammable, or explosive properties…” It may be a surprise to look at the list and see what the values are! The threshold quantities range from 100 lbs. for Ozone to 5,000 lbs. for Methyl Mercaptan to 15,000 lbs. for Methyl Chloride.
The same Highly Hazardous Chemicals and threshold quantities apply to RMP. The major differences between being covered by PSM and RMP lie in the exclusions. So what is excluded? For PSM, exclusions are all fluids at a retail facility, fluids used solely for fuel, flammable liquids stored in atmospheric tanks, oil and gas facilities that are generally not manned, and state and local governments. The RMP standard has a different list of exclusions. These include ammonia when held by a farmer for use at a farm, flammable fluids used as a fuel or for sale at a retail facility as a fuel, and transportation including storage incident to transportation. These overlap to some extent, however it is possible to be covered under PSM and not under RMP and vice versa.