StacksVerified U.S. regulatory reference

40 CFR §355.15

Verified against eCFR.gov as of June 20, 2026View official text on eCFR.gov ↗
EHSs that are in solid form are subject to one of two different TPQs (for example, TPQs may be listed as 500/10,000 pounds), both of which are listed in Appendices A and B of this part. Here is how to determine which of the two listed TPQs you must use for an EHS present at your facility in solid form:
  1. (a)Use the lower TPQ from Appendices A and B of this part if the solid:
    1. (1)Is in powdered form and has a particle size less than 100 microns;
    2. (2)Is in solution;
    3. (3)Is in molten form; or
    4. (4)Meets the criteria for a National Fire Protection Association (NFPA) rating of 2, 3 or 4 for reactivity.
  2. (b)If the solid does not meet one of the criteria in paragraph (a) of this section, then the TPQ is 10,000 pounds.