An official website of the United States government.

What is a reactive and non-reactive solid EHS?

Reactive solid means any extremely hazardous substance denoted with “a” in the “Notes” column in Appendix A or B of 40 CFR 355. Reactive solids are more likely than other solids to be dispersed into the air due to the energy or heat created from their reactivity with water or air. EHSs that are reactive solids have only one TPQ assigned (no 10,000 lb TPQ) regardless of their physical state, form or particle size.

Non-reactive solid means any substance listed in Appendix A or B of 40 CFR 355 with two threshold planning quantity values, the higher TPQ being 10,000 pounds.