The Pipeline and Hazardous Materials Safety Administration, Office of Hazardous Materials Safety (OHMS) provides written clarifications of the Hazardous Materials Regulations (HMR; 49 CFR Parts 100-185) in the form of interpretation letters.
These letters reflect the agency's current application of the HMR to the specific facts presented by the person requesting the clarification. Interpretations are one form of Guidance provided by OHMS.
Interpretations do not create legally-enforceable rights or obligations and are provided to help the public understand how to comply with the HMR.
OHMS regularly reviews interpretations on this site for accuracy and applicability. Interpretation letters from the last ten years are published here to provide the public with a greater awareness and understanding of the HMR. Letters of interpretation which are found to be inaccurate or no longer applicable are removed and may be revised and reissued if warranted. Letters which do not appear on this website may no longer be valid.
We welcome feedback from the hazmat safety community to ensure the most recent and accurate letters of interpretation are provided here. Questions or concerns about a specific letter or topic should be directed to the Hazardous Materials Information Center.