Strong outer packaging & conditions normally incident to transportation

Written on: November 1, 2016 by SprayTM

The U.S. Dept. of Transportation’s (DOT) Pipeline & Hazardous Materials Safety Administration (PHMSA) refers to “strong outer packaging” and “conditions normally incident to transportation” throughout Title 49, Code of Federal Regulations (CFR), subchapter C Hazardous Materials Regulations (HMR). In particular, 49 CFR §173.306, the section applicable to aerosols and limited quantities of compressed gases, refers to “strong outer packaging” fourteen times. I counted the term “conditions normally incident to transportation” in the HMR no fewer than 30 times.

Interestingly enough, one term is used to define the other. Regulation 49 CFR §171.8 defines a “strong outer packaging” as:

…the outermost enclosure that provides protection against the unintentional release of its contents. It is a packaging that is sturdy, durable, and constructed so that it will retain its contents under normal conditions of transportation. In addition, a strong outer packaging must meet the general packaging requirements of subpart B of part 173 of this subchapter but need not comply with the specification packaging requirements in part 178 of the subchapter. For transport by aircraft, a strong outer packaging is subject to §173.27 of this subchapter. The terms “strong outside container” and “strong outside packaging” are synonymous with “strong outer packaging.”

Curiously, however, DOT never defines the term “conditions normally incident to transportation.”

Strong Outer Packaging
A “strong outer packaging” must be…sturdy, durable and constructed so that it will retain its contents….and meet the general packaging requirements…of 49 CFR 173 subpart B and, for transport by air, meet the requirements of 49 CFR §173.27.

49 CFR §173.24 (General requirements for packagings and packages), section 173.24(b) requires that:

There will be no identifiable (without the use of instruments) release of hazardous materials to the environment;

The effectiveness of the package will not be substantially reduced. For example, impact resistance, strength, packaging compatibility, etc. must be maintained for the minimum and maximum temperatures, changes in humidity and pressure, and shocks, loadings and vibrations, normally encountered during transportation;

There will be no mixture of gases or vapors in the package which could, through any spontaneous increase of heat or pressure, significantly reduce the effectiveness of the packaging; and

There will be no hazardous material residue adhering to the outside of the package during transport.

Certainly, requirements (a), (c) and (d) listed above seem logical and Item (b) seems reasonable, as well. However, it is much harder to quantify the minimum and maximum temperatures, changes in humidity and pressure, and shocks, loadings and vibrations that are normally encountered during transportation.

Transportation by Air
Regulation 49 CFR §173.27(c) requires that packagings be designed and constructed to prevent leakage that may be caused by changes in altitude and temperature during transportation aboard aircraft. These provisions also require that:

Packaging for which retention of liquid is a basic function must be capable of withstanding without leakage the greater of:

 (i)         An internal pressure which produces a gauge pressure of not less than 75 kPa (11 psig) for liquids in Packing Group III of Class 3 or Division 6.1; or 95 kPa (14 psig) for other liquids; or

 (ii)        A pressure related to the vapor pressure of the liquid to be conveyed, determined by one of the following:

 (A)       The total gauge pressure measured in the receptacle (i.e., the vapor pressure of the material and the partial pressure of air or other inert gases, less 100 kPa (15 psia)) at 55°C (131°F), multiplied by a safety factor of 1.5; determined on the basis of a filling temperature of 15°C (59°F) and a degree of filling such that the receptacle is not completely liquid full at a temperature of 55°C (131°F) or less;

 (B)       1.75 times the vapor pressure at 50°C (122°F) less 100 kPa (15 psia); or

 (C)       1.5 times the vapor pressure at 55°C (131°F) less 100 kPa (15 psia).

Regulation 49 CFR §173.27(d) requires the body and closures of any packaging to be constructed such that they will adequately resist the effects of temperature and vibration occurring in conditions normally incident to air transportation. There it is again: normally incident to transportation.

Conditions Normally Incident to Transportation
I poured through the plethora of U.S. DOT interpretations trying to find a definition of the term “conditions normally incident to transportation” and found nothing. Interesting enough, however, I did find a more quantitative definition of the elusive term in the unlikeliest of places—10 CFR §71.71 are regulations that apply to shipments of radioactive material. Title 10, Code of Federal Regulations, section 71.71 defines Normal Conditions of Transport as:


Heat An ambient temperature of 38°C (100°F) in still air.
Cold An ambient temperature of -40°C (-40°F) in still air and shade.
Reduced External Pressure An external pressure of 25 kPa (3.5 psi) absolute.
Increased External Pressure An external pressure of 140 kPa (20 psi) absolute.
Vibration Vibration normally incident to transport.
Water Spray A water spray that simulates exposure to rainfall of approximately 5cm/h (2in/h) for at least one hour.
Free Drop A free drop through the distance specified below onto a flat, essentially unyielding, horizontal surface, striking the surface in a position for which maximum damage is expected.
Corner Drop A free drop onto each corner of the package in succession, or in the case of a cylindrical package onto each quarter of each rim, from a height of 0.3m (1ft) onto a flat, essentially unyielding, horizontal surface.
Compression The package must be subjected, for a period of 24 hours, to a compressive load applied uniformly to the top and bottom of the package in the position in which the package would normally be transported. The compressive load must be the greater of the following:

The equivalent of five times the weight of the package; or

The equivalent of 13 kPa (2psi) multiplied by the vertically projected area of the package.

Penetration Impact of the hemispherical end of a vertical steel cylinder of 3.2cm (1.25in) diameter and 6kg (13lbs) mass, dropped from a height of 1m (40in) onto the exposed surface of the package that is expected to be most vulnerable to puncture. The long axis of the cylinder must be perpendicular to the package surface.

Arguably, their definition of heat seems too low given that cities such as Phoenix, Las Vegas, Yuma and Palm Springs have average highs over 100°F (38°C) during the summer months. According to the Guinness Book of World Records, the official highest recorded temperature is now 56.7°C (134°F), which was measured on July 10, 1913 at Greenland Ranch, Death Valley, CA. The average daily maximum temperature in the hottest inhabited place on Earth (Dallol, Ethiopia) is 41.1°C (106°F).

Nevertheless, we all know, intuitively, that the average temperature inside a closed freight container or tractor trailer in the summer is closer to 130°F. Maybe this is why the reference temperature of +55°C (131°F) is used throughout the HMR? Therefore, shippers would be wise to consider the term “Heat” to include temperatures of up to +55 °C (131°F).

With respect to “Reduced External Pressure,” 10 CFR §71.71 defines it as being as low as 3.5psia. However, most commercial aircraft are limited to a maximum altitude of 45,000 ft. Temperatures at these altitudes are typically around -40°C (-40°F). At that reference temperature and altitude, the ambient air pressure would actually be 1.21 psi. Indeed, the U.S. DOT’s HMR refers to a 95 kPa pressure differential test being required for the inner packagings of combination packagings tendered for air transport. A pressure drop of 95 kPa at max altitude would mean an ambient air pressure of less than 1.0 psia. Therefore, shippers should also consider that “Reduced External Pressure” could be as low as 0.74 psia (or -70°C at 45,000 ft).

With respect to vibration, I would recommend that shippers consult 49 CFR §178.608, which outlines requirements for the vibration test performed on UN-approved fiberboard boxes. Since the regulations state that non-specification packagings must be capable of passing the prescribed tests, it stands to reason that we refer to the test criteria in the vibration standard.

Vibration Test
Three sample packagings, selected at random, must be filled and closed as for shipment. The three samples must be placed on a vibrating platform that has a vertical or rotary double-amplitude (peak-to-peak displacement) of one inch. The packages should be constrained horizontally to prevent them from falling off the platform, but must be left free to move vertically, bounce and rotate. The test must be performed for one hour at a frequency that causes the package to be raised from the vibrating platform to such a degree that a piece of material approximately 1.6mm (0.063 inch) thickness (such as steel strapping or paperboard) can be passed between the bottom of any package and the platform.

Pass/Fail Criteria
A package passes the above tests if there is no rupture or leakage from any of the samples. No test sample should show any deformation that could adversely affect transportation safety or any distortion liable to reduce packaging strength.

Certainly, if the conditions outlined herein were considered, one could argue that the packaging to be used was capable of meeting the “conditions normally incident to transportation,” and would, therefore, be defined as a “strong outer packaging” and approved for the transport of these types of dangerous goods.

For additional information on strong outer packagings and conditions normally incident to transportation, you may contact the U.S. DOT PHMSA website at or call ShipMate, Inc. at (310) 370-3600.