Vermiculite as an Absorbent and Cushioning Material
Pipeline and Hazardous Materials Safety Administration · Dec 1, 2005 · Reference No. 05-0102
Interprets: 49 CFR § 173.24, 49 CFR § 173.24a, 49 CFR § 173.27, 49 CFR § 178.601
Reggie’s quick take
A company asked whether vermiculite that was already used in one shipment can be reused as absorbent and cushioning material in UN specification packagings, and whether a different granule size from the one used in the packaging's tests can be swapped in. The agency says previously used vermiculite may be reused if it has not been compromised and can still secure, cushion and absorb as § 173.24, 173.24a, 173.27 and 178.601 require. On a different grade, the agency says the packaging must still meet its certified standard and the material must match the tested design. Without test data showing the grades cushion about the same, the agency cannot confirm a swap is allowed without more testing.
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 requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) regarding the use of used vermiculite as an absorbent and cushioning material in UN specification packagings. Specifically, you asked whether the HMR authorizes the reuse of vermiculite that was used in a previous shipment. You also asked whether a grade of vermiculite that varies (such as smaller or larger granules) from the grade used when the packaging was tested may be used when shipping hazardous materials.
Previously used vermiculite may be used in subsequent packagings provided it has not been compromised and can perform the securing, cushioning and absorbent functions required by § 173.24, 173.24a, 173.27, and 178.601, as applicable.
With respect to whether a different grade of vermiculite may be used if the packaging was tested with a smaller or larger grade of vermiculite, the packaging must meet the standard to which it is certified and the material must be of the same type or design as used in the tested design type. Without specific test data indicating the two grades of vermiculite have similar cushioning properties, it is not possible for us to make a determination that your samples of vermiculite are of the same type and may be interchanged without further testing.
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.