Aerosols: Is Further Harmonization Needed?

With so much focus over the years on harmonizing the dangerous goods regulations, one commodity that can definitely benefit from a focused review is the entry for aerosols.  This is particularly a concern relative to U.S. regulations, where the definition for aerosols is not aligned with the international definition.  In §171.8 of the Hazardous Materials Regulations (HMR) the term “Aerosol” is defined as

Any non-refillable receptacle containing a gas compressed, liquefied or dissolved under pressure, the sole purpose of which is to expel a nonpoisonous (other than a Division 6.1 Packing Group III material) liquid, paste, or powder and fitted with a self-closing release device allowing the contents to be ejected by the gas.”

This definition is inconsistent with the definition of an aerosol found in the United Nations Regulations on the Transport of Dangerous Goods (UN Model Regulations), the International Maritime Dangerous Goods Code (IMDG Code), the International Civil Aviation Organization Technical Instructions on the Safe Transport of Dangerous Goods by Air (ICAO TI), and the European Agreement Concerning the International Carriage of Dangerous Goods by Road (ADR). The main difference is that the international regulations do not prohibit an aerosol container from being filled solely with a gas.  This disharmony leads to a number of reclassification and marking problems for shippers and carriers alike.

U.S. regulators spanning back to the days of Alan Robert’s tenure have taken the position that an aerosol container filled with pure butane, for instance, should not be allowed to be reclassed under the proper shipping name “Aerosol”.  U.S. regulators have indicated on numerous occasions that this would compromise safety and, in particular, emergency response efforts by masking the true hazards of the product contained in the aerosol receptacle (Note: Wrong or right, I have to admit I may have made the statement once or twice during my tenure as a regulator).  Nevertheless, there really are no standards related to how much propellant gas can be contained to expel the liquid, powder or paste.  I have been told that products currently on the market have upwards of 95 percent propellant gas which, in many cases, consists of isobutane, a highly flammable substance.  However, there are also many consumer products that pose very little risk in transportation, such as air dusters, and refrigerant gases (e.g. 1,1,1,2-Tetrafluoroethane (R-134a)) that could certainly benefit from harmonization and a fresh look at the HMR requirements.  In the United States, the more restrictive definition requires 1,1,1,2-Tetrafluoroethane (R-134a) to be offered as “UN3159 – 1,1,1,2-Tetrafluoroethane.” These products must be transported under special permits, which we all know are cumbersome to acquire and put to use in practice.

Other areas ripe for improved harmonization include:

  • Aerosol leak testing;
  • 2P/2Q specifications, which are not aligned with European standards;
  • Limited quantity provisions (there are some disconnects in §173.306 with international regulations);
  • Regulations that have multiple entries accounting for every possible variation on the contents and subsidiary risks (e.g. ICAO TI) while others (e.g. UN Model Regulations, IMDG Code) have a single entry in the dangerous goods list; and
  • Clarification of the difference between the definition of an aerosol and small gas receptacles.

Exceptions for aerosols and packing requirements are found in §173.306. In particular, subparagraphs §173.306(a)(3) and (5) provide exceptions for aerosols in metal and plastic non-refillable containers, while paragraph (i) allow them to be reclassified as ORM-D products.  This, of course, will be phased out of the HMR and aerosols will eventually need to be shipped as limited quantities.  However, the HMR limited quantity provisions are more conservative than special provision 277 in the Model Regulations.  Over the years, §173.306 has become extremely complicated with requirements for many commodities addressed (e.g. shock absorbers, aerosols, small gas receptacles, refrigerating machines, etc.).  It would make good sense to create specific packaging sections for each of these commodities to enhance clarity, harmonization, safety and compliance.

A rewrite of §173.306 could also take into account the effort of codifying numerous special permits (SP-10232, SP-14188, and SP14286 to name a few), which would result in reducing burden on government and industry and would be consistent with the mandate in the latest hazmat reauthorization bill, Moving Ahead for Progress in the 21st Century (MAP-21). MAP-21 requires the agency to conduct a review of special permits that have been in effect for 10 or more years to determine if they can be converted to regulations; this review takes into account the safety record, suitability of the provisions and rulemaking activity in related areas.  The aforementioned special permits would certainly fit the criteria.

On Sept. 13, 2012, the Council on Safe Transportation of Hazardous Articles (COSTHA) filed a petition with the Pipeline and Hazardous Materials Safety Administration (PHMSA) proposing to harmonize the HMR with applicable international regulations with regards to the classification, testing, and transport of aerosols.  In the petition COSTHA requested that PHMSA:

  • Modify the definition of an aerosol to include certain non-refillable gas containers with or without a liquid, paste, or powder; and
  • Permit alternate testing methods to the current hot water bath test in §173.306(a)(3)(v), such as those identified in Chapters and of the UN Model Regulations.

COSTHA should be applauded for their efforts in this regard.  This petition was one long overdue and one that will hopefully be taken up and given serious consideration by PHMSA, as it is consistent with the Retrospective Regulatory Review (RRR) initiative that was enacted in accordance with Presidential Executive Order 13563. Providing harmonized requirements for aerosols will allow many products to be marked, labeled, and documented for transport in the U.S. as they would be for international transportation, thus reducing the cost and burden of remarking and re-documenting shipments destined for distribution in other countries.  In a follow-up to this article, we will discuss how the differences in the shipping description listed in the various regulations result in problems for shippers worldwide.


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  1. Desmond WAIGHT (DGSA - All classes by road/rail/inland waterway) said:

    Fully agree that USA should come in line with international provisions(accepting that USA have the right to try and amend the international provisions in line with their thinking). In UK I constantaly see butane fuel containers that are aerosols (in that they have a release device that sticks out at the top – althrough no spray nozzle- and which needs a cap, as specified in the packaging provisions, to prevent inadvertent activation) but which are wrongly classified as UN2037 gas cartidges (which do not have release devices per UN – and which hence do not need a protective cap). Most of these come from Far East where the wrong classification results from the USA being out of line (whether rightly or wrongly) with the interantional provisions of IMDG Code and ADR