Applicability of the HMR to a household smoke detector
Pipeline and Hazardous Materials Safety Administration · Sep 10, 2008 · Reference No. 08-0144
Interprets: 49 CFR § 173.422, 49 CFR § 173.424
Reggie’s quick take
A company asked whether a household smoke detector with Americium 241 can ship as non-hazardous if it meets § 173.424(d), which covers radiation levels below 0.1 mSv/hour (10 mrem/hour) at 10 cm from the unpackaged device. PHMSA said no. Such a detector is regulated as Class 7 (radioactive) material. It can still use the § 173.424(d) exception, but only if its radiation level at 10 cm from any point on the surface is within that limit, and the package is otherwise prepared as § 173.422 requires and meets all of § 173.424. The detector would count as non-hazardous only if it is not radioactive material and falls in no other hazard class under the HMR.
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 May 22, 2008 letter requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) regarding the applicability of the HMR to a household smoke detector. Specifically, you ask whether a household smoke detector, containing Americium 241, can be shipped as a non hazardous material if it meets the provisions of § 173.424(d). You state that the household smoke detector produces less than 0.1 mSv/hour (10 mrem/hour) from any point of its external surface.
The answer is no. A household smoke detector as described above would be regulated as Class 7 (radioactive) material. Section 173.424(d) states, in part, that a radioactive instrument or article and its packaging is excepted from the specification packaging, shipping paper and certification, marking and labeling (except for the UN identification number marking requirement described in § 173.422(a)) requirements if:
The radiation level at 10 cm (4 in) from any point on the external surface of any unpackaged instrument or article does not exceed 0.1 mSv/hour (10mrem/hour).
In accordance with § 173.424(i) the package must be otherwise prepared for shipment as specified in § 173.422 and must comply with all the provisions of § 173.424 when transported in commerce.
However, if your smoke detector containing Americium 241 does not meet the definition of a radioactive material and does not meet the definition of any other hazard class as defined in the HMR it would be considered non-hazardous.
I hope this information is helpful. If you have further questions, please do not hesitate to contact this office.
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.