Containment System for Radioactive Materials
Pipeline and Hazardous Materials Safety Administration · Sep 29, 2006 · Reference No. 06-0189
Interprets: 49 CFR § 73.403, 49 CFR § 173.410, 49 CFR § 173.412, 49 CFR § 173.415, 49 CFR § 173.465, 49 CFR § 173.466, 49 CFR § 178.350
Reggie’s quick take
A company asked whether a passive HEPA vent can be placed in a Type A radioactive materials package so the package still meets the requirement to keep its contents under reduced air pressure (25 kPa, or 3.6 psi), as long as no radioactivity escapes. PHMSA says the rules do not ban vents in Type A packagings for Class 7 (radioactive) materials. The package must still be an authorized packaging for that material, meet any applicable design specification, and follow the general packaging rules in Part 173, Subpart B. The vented Type A packaging must also meet § 178.350 and the related rules in §§ 173.403, 173.410, 173.412, 173.415, 173.465 and 173.466.
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 August 15, 2006 letter requesting clarification regarding the applicability of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) to HEPA vents. Your question pertains to § 173.412(f) which requires the containment system to retain its radioactive contents under the reduction of ambient pressure to 25 kPa (3.6 psi). Specifically, you ask if a passive HEPA vent may be installed in a Type A package to meet the pressure requirement in § 173.412(f) as long as the resultant containment system would not release any radioactivity to the environment.
The HMR do not prohibit the use of vents in Type A packagings containing Class 7 (radioactive) materials. However, the packaging must be an authorized packaging for the Class 7 (radioactive) material under the HMR, meet the HMR design specification (if applicable), and comply with the general packaging requirements in Part 173, Subpart B. The Type A packaging, with the vent, must meet the design and construction requirements in § 178.350, which also requires compliance with § 173.403, 173.410, 173.412, 173.415, 173.465 and 173.466.
I hope this information is helpful.
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.