Closure requirements for packagings
Pipeline and Hazardous Materials Safety Administration · Mar 17, 2008 · Reference No. 07-0174
Interprets: 49 CFR § 173.27
Reggie’s quick take
A company that ships liquid hazardous materials in combination packages asked whether the closure rules apply when each inner bottle has a foil induction seal and a screw cap on top. The company thought the seal was the real closure, so the screw-cap rule in § 173.27(d) would not apply. PHMSA disagrees. Because the tested package has bottles fitted with screw caps, each screw cap must be secured under § 173.27(d), even when an induction seal is also used. The cap is secured properly if it cannot loosen from vibration or big temperature changes.
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 31, 2007, email requesting clarification on closure requirements for packagings containing hazardous materials transported by aircraft in accordance with the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180).
According to your letter, your company ships liquid hazardous material in combination packages with inner receptacles consisting of 4 ounce or 16 ounce bottles. The closures consist of an ultrasonically sealed foil and plastic material (induction seal) and a screw cap fitted over the seal. The combination package is tested and certified to conform to the UN packaging requirements of Part 178 and the additional requirements of § 173.27. Section 173.27(d) requires each screw-type closure on any packaging to be secured to prevent the closure from loosening due to vibration or substantial change in temperature. It is your understanding that since the bottle is physically sealed without the screw cap, the closure is the induction seal, not the screw cap and the requirements of § 173.27(d) would not apply.
Since the tested combination package has inner receptacles fitted with a screw cap, the screw cap must be secured in accordance with § 173.27(d). This applies regardless of whether the inner receptacle also employs an induction seal. If the screw-cap closure is secured in a manner that prevents it from loosening due to vibration or substantial change in temperature, the requirement of § 173.27(d) has been met.
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.