July 2014

Take a Bath Before You Take a Bath…

Readers are probably already aware that there is a significant difference in how “aerosols” are defined by the U.S. Dept. of Transportation’s (DOT) Pipeline & Hazardous Materials Safety Administration (PHMSA) and the rest of the world. However, just in case, I will highlight this and other differences in the requirements.

Different Definitions

According to Title 49, Code of Federal Regulations, subchapter C, §171.8 an aerosol is:

“…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.”

By contrast, the U.N. Model Regulations, International Maritime Dangerous Goods (IMDG) Code, International Civil Aviation Organization (ICAO) Technical Instructions for the Transport of Dangerous Goods by Air and other regulatory references define an aerosol as:

“non-refillable receptacles meeting the provisions of [the packaging regulations], made of metal, glass or plastics and containing a gas compressed, liquefied or dissolved under pressure, with or without a liquid, paste or powder, and fitted with a release device allowing the contents to be ejected as solid or liquid particles in suspension in a gas, as a foam, paste or powder or in a liquid state or in a gaseous state.”

Consequently, this may present some serious issues when importing or exporting certain compressed gases such as butane cartridges and lighter refills, refrigerants (e.g., 1,1,1,2-tetrafluoroethane) and spray dusters. For example, under the provisions of the IMDG Code, R-134a (1,1,1,2-tetrafluoroethane) may be re-classed and described as UN1950, AEROSOLS, 2.2 and offered as a limited quantity when in metal receptacles of not more than one liter in volume. However, that very same product could NOT be offered as a limited quantity in receptacles between 120–1000mL in the U.S. Title 49 CFR 171.23(b)(1) permits the IMDG Code to be used within the U.S., but specifically requires that compressed gases be limited to 4 fl. oz. (120mL).

Title 49 CFR §171.23(b)(1) states:

“Except for a limited quantity of a compressed gas in a container of not more than four fluid ounces capacity meeting the requirements in § 173.306(a)(1) of this subchapter, the proper shipping name “Aerosol,” UN1950, may be used only for a non-refillable receptacle containing a gas compressed, liquefied, or dissolved under pressure the sole purpose of which is to expel a nonpoisonous (other than Division 6.1, Packing Group III material) liquid, paste, or powder and fitted with a self-closing release device (see § 171.8).”

It is interesting to note, however, that the IMDG Code limits UN3159, 1,1,1,2-TETRAFLUORETHANE, 2.2 to 120mL in order to take advantage of the limited quantities. Although this quantity limitation is consistent with 49 CFR subchapter C, the IMDG Code allows you to reclassify the product as an aerosol, thereby enjoying the “added” volume, whereas 49 CFR does not.


Another important difference between 49 CFR subchapter C and the international standards, based on the U.N. Model Regulations, is the use of an alternative to the hot water bath test. The IMDG Code, for example, in section of the 36th Amendment permits alternative methods which provide an equivalent level of safety, with the approval of the competent authority, and which conform to the requirements outlined in the subsequent sections of the Code.

Provided the requirements of are met, and the competent authority has authorized the alternative test method, aerosols outside the U.S. need not be tested in a hot water bath. The requirements include a quality system, pressure and leak testing before filling and testing of the aerosol after filling. For convenience, I have transcribed the requirements below:

Quality system (

Aerosol dispenser fillers and component manufacturers shall have a quality system. The quality system shall implement procedures to ensure that all aerosol dispensers that leak or that are deformed are rejected and not offered for transport. The quality system shall include:

a)      a description of the organizational structure and responsibilities;

b)      the relevant inspection and test, quality control, quality assurance and process operation instructions that will be used;

c)      quality records, such as inspection reports, test data, calibration data and certificates;

d)     management reviews to ensure the effective operation of the quality system;

e)      a process for control of documents and their revision;

f)       a means for control of non-conforming aerosol dispensers;

g)      training programs and qualification procedures for relevant personnel; and

h)      procedures to ensure that there is no damage to the final product.

An initial audit and periodic audits shall be conducted to the satisfaction of the competent authority. These audits shall ensure the approved system is and remains adequate and efficient. Any proposed changes to the approved system shall be notified to the competent authority in advance.

Pressure and leak testing of aerosol dispensers before filling (

Every empty aerosol dispenser shall be subjected to a pressure equal to or in excess of the maximum expected in the filled aerosol dispensers at 55°C (50°C if the liquid phase does not exceed 95% of the capacity of the receptacle at 50°C). This shall be at least two-thirds of the design pressure of the aerosol dispenser. If any aerosol dispenser shows evidence of leakage at a rate equal to or greater than 3.3 x 10-2 mbar·L·s-1 at the test pressure, distortion or other defect, it shall be rejected.

Testing of the aerosol dispensers after filling (

Prior to filling, the filler shall ensure that the crimping equipment is set appropriately and the specified propellant is used. Each filled aerosol dispenser shall be weighed and leak tested. The leak detection equipment shall be sufficiently sensitive to detect at least a leak rate of 2.0 x 10-3 mbar·L·s-1 at 20°C. Any filled aerosol dispenser which shows evidence of leakage, deformation or excessive mass shall be rejected.

Special Permits Required

In order to avoid the hot water bath test (for other than certain foodstuffs and certain non-flammable aerosols in plastics receptacles), the filler or manufacturer must apply for and obtain a DOT Special Permit, which can be quite a daunting task (see Spray, April 2013). Special Permit applicants must be able to demonstrate an equivalency of safety and will generally be denied a permit based on a “leveling of the playing field” approach.

It is important that you can demonstrate that the methods, procedures and equipment used in pre-filling and post-filling testing will satisfy the DOT’s safety concerns.

Shippers, fillers and manufacturers are strongly cautioned to ensure that they review the U.S. rules very carefully and confirm that aerosols have been subjected to and pass the hot water bath test, or an alternative method has been approved and documented in a DOT Special Permit, which is generally required to travel with the other shipping documents and/or be marked on the aerosol packaging.

Failure to comply with these provisions will subject inbound loads to forfeiture and/or destruction and significant penalties, which can be in the tens or even hundreds of thousands of dollars. Additionally, import shipments that do not conform to the U.S. standards for aerosols because they have either not been subjected to the hot water bath and/or do not meet the U.S. definition of aerosols may be subjected to additional penalties because the required marks and labels or documents, for example, reflect the change in classification and are not appropriate for transport within the U.S. as aerosols.

If you have any questions regarding the testing or transportation requirements for aerosols, contact the author at [email protected] or (310) 370-3600.