Overpack Letter of Interpretation Update
After 10 months of back-and-forth with the US Department of Transportation (DOT) Pipeline and Hazardous Materials Safety Administration (PHMSA) regarding Letter of Interpretation No. 24-0010, we finally have some conclusions regarding the use of Overpack for aviation compressed gas cylinders.
Tym’s Request Resulted in Revised Letter of Interpretation
On January 3, 2025, the agency issued a revised Letter of Interpretation No. 24-0010R in response to our request for clarification outlined here.
The revised letter of interpretation clarified our main points regarding the proper use of Overpack on aviation articles containing DOT specification cylinders but failed to respond to a specific issue regarding cylinder types not listed in 49 CFR 173.301(a)(9).
Recap on Cylinder Marking and Labeling Requirements
Remember that 49 CFR 172.400(a)(1) requires all non-bulk packages (i.e. compressed gas cylinders) to have the proper hazmat label and 49 CFR 172.301(a)(1) requires all cylinders to have the proper “marking,” such as UN number and proper shipping name.
However, most aircraft cylinder assemblies fail to meet this requirement as part of their design.
Keep in mind that the definition of “package” is the DOT specification cylinder itself and not the box it goes in, unless you have a “combination package.”
Follow-Up Question to DOT
Our next question to DOT PHMSA was simple: “Is there any regulation which prohibits using a combination package to satisfy 49 CFR 172.400(a)(1) and 49 CFR 172.301(a)(1)?”
Their answer was equally simple… just kidding, lol.
DOT Response
The actual response was as follows (our emphasis in bold type):
DOT 3AA specification cylinders cannot be used as combination packaging as they are deemed a package. DOT specification cylinders not specifically listed in § 173.301(a)(9) that are further packaged in a fiberboard box meet the configuration of an overpack and the “OVERPACK” marking is required unless the markings representative of each package type contained in the overpack are visible from outside of the overpack. Section 173.25 outlines the requirements for overpacks and 171.8 provides the definition of an overpack. DOT 3HT specification cylinders are listed in 173.301(a)(9) and are required to be packaged in a ‘strong outer packaging’. This configuration must be marked ‘inner packagings conform to the prescribed specifications’. This configuration is required by this section and does not meet the definition of an overpack.
Practical Takeaways
The takeaway here is that aviation parts with DOT cylinders installed must be categorized by at least two types and marked/labeled as appropriate. Keep in mind that all aviation articles require additional packaging of some sort (don’t even get us started on ATA Specification 300). The two categories are as follows:
- Those that have cylinders with specifications listed in 49 CFR 173.301(a)(9)
- Those that have cylinders with specifications NOT listed in 173.301(a)(9)
While not true in every circumstance, the requirement can be summarized as follows:
- For articles in category 1 – Do not mark as Overpack. Instead mark with “inner packagings conform to the prescribed specifications”
- For articles in category 2 – Mark with Overpack (and make sure it meets the requirement for an Overpack)
Required Cylinder Marking and Labeling
We appreciate clarification from the DOT that “specification cylinders cannot be used as combination packaging.” This makes the requirement to mark/label cylinders in category 2 above very clear. Again, not the outer package, but the cylinder itself.
Additional Problems for Shippers
The issue is that most aircraft articles containing cylinders do not include a compliant mark or label as part of the design. Therefore, each shipper is required to add required hazardous materials marking and labeling to the cylinder, while also ensuring the requirements of 14 CFR are respected.
This also means navigating customer expectations regarding the configuration of articles they expect will (visually) meet the original design. An additional label not listed in maintenance data, drawings, etc. will likely lead to questions and perhaps rejection during the receiving inspection process. Merely adding an additional decal may not be as easy as it sounds just based on the size of required labels and space available on the cylinder, for example.
Tym’s Solutions
Tym’s is uniquely qualified to assist in finding a solution that works for your specific circumstance. Familiarity with complex regulations and practical experience in the industry allow us to offer simple solutions for complicated compliance issues such as these. Reach out today for a no-obligation consultation.