Minimum thickness requirements for steel drums
Pipeline and Hazardous Materials Safety Administration · May 5, 1995 · Reference No. 95-0199
Interprets: 49 CFR § 173.28
Reggie’s quick take
A reader asked whether the decimal places after the last whole number in the § 173.28(b)(4) drum thickness table can be treated as zeros. PHMSA says yes for the metric figures, which are the legal standard, but not for the U.S. customary figures, which are for information only. For example, a required 0.8 mm minimum means the steel can be 0.8000 mm thick, which converts to 0.0315 inch under § 171.10. PHMSA also admits its earlier reply gave 0.0300 inch, which was wrong. The letter notes a pending petition to restore a 0.82 mm to 1.09 mm minimum thickness note.
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 to clarify my May 26, 1994, reply to your inquiry concerning minimum thickness requirements for steel drums which are to be reused. A further review of this issue indicates a need to qualify my previous response.
In your letter, you asked whether, for the minimum thicknesses specified in the table in 49 CFR 173.28(b)(4), the decimal places following the last whole number indicated can be assumed to be zeroes. This is true for the metric measurement, which is the regulatory standard. However, this is not true for the U.S. customary measurement, which is provided for information only. For example, where a minimum thickness of 0.8 is required, the steel can have a minimum thickness of 0.8000 mm. Based on the conversion table contained in § 171.10, the equivalent U. S. customary measurement is 0.0315 inch. My previous response included the U.S. customary measurement of 0.0300 inch, which is not correct.
I apologize for any confusion my earlier response may have caused, and hope this matter is now resolved. We have received and are considering a petition for reconsideration to the Docket HM-215A final rule (December 29, 1994; 59 FR 67390) to restore the minimum thickness requirement in the note to the 173.28(b)(4) table to 0.82 mm to 1.09 mm. These were the minimum thickness requirements adopted in the December 1990 final Rule under Docket HM-181.
Please contact this office if you require additional assistance.
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.