Packaging Requirements for Materials Poisonous by Inhalation
Pipeline and Hazardous Materials Safety Administration · May 16, 2000 · Reference No. 00-0102
Interprets: 49 CFR § 173.227(b)(ii)
Reggie’s quick take
A company asked whether putting a bead of silicone caulk around the bung closure on a container of poisonous-by-inhalation material meets § 173.227(b)(ii). That section requires the closure to be held in place by any means that prevents it from backing off or loosening from impact or vibration during transport. PHMSA said the caulk method the company described is acceptable.
Written by AI (Claude) on Oct 22, 2026. Robots make mistakes and leave things out, so the letter below is what counts. Not legal advice.
This is in response to your letter of April 12, 2000, requesting clarification on the packaging requirements for materials poisonous by inhalation under the Hazardous Materials Regulations (HMR; 49 CFR Parts 171 -180).
The packaging requirements of § 173.227(b)(ii) state that the closure must be physically held in place by any means capable of preventing back-off or loosening of the closure by impact or vibration during transportation. You ask whether using a bead of silicone caulk around the bung closure meets the provisions of § 173.227(b)(ii).
The means you have described for physically holding a bung closure in place is acceptable.
A letter of interpretation applies the regulations to the facts the requester described. It isn’t a regulation and isn’t legal advice. The agency’s copy.