Highly hazardous chemical
A toxic, reactive, flammable or explosive substance that brings a process under OSHA's Process Safety Management standard.
Definition, in the source's words
29 CFR 1910.119(b)(opens ecfr.gov in a new tab)“Highly hazardous chemical means a substance possessing toxic, reactive, flammable, or explosive properties and specified by paragraph (a)(1) of this section.”
What it means
Paragraph (a)(1) covers processes with a chemical listed in Appendix A at or above its threshold quantity, and processes with 10,000 pounds or more, on site in one location, of a Category 1 flammable gas or a flammable liquid with a flashpoint below 100°F (37.8°C), with listed exceptions such as fuels used solely for workplace consumption.
Example
A plant keeps 15,000 pounds of propane feeding a process. Propane is a Category 1 flammable gas and 15,000 pounds is over the 10,000-pound threshold, so the process is covered by PSM: process hazard analysis, operating procedures, management of change and the rest.
Where it appears on the exam
ASP: ASP11 Domain 2, Safety Programs and Concepts
Practice: Process Safety Management
CSP: CSP11 Domain 1, Advanced Application of Safety Principles
Practice: Process Safety Management, Process Hazard Analysis
Questions
- What's the PSM threshold for flammable liquids and gases?
- 10,000 pounds or more on site in one location of a Category 1 flammable gas, or of a flammable liquid with a flashpoint below 100°F, under 1910.119(a)(1)(ii), with the exceptions listed there.
Related
Checked 2026-10-16. Spot a problem? Email hello@passcited.com.