Lately, there have been several questions surrounding hazardous shipments, especially regarding the landfill gas samples and the standard 6 L Summa canisters. I have touched on these issues before and hoped they were filtering out into the field to replace the misinformation, which still seems to be all too prevalent.
1. The DOT regulations are very clear on what can be shipped and how, so if there is any question you should contact them. I know a lot of the shipping companies have trained people for hazardous shipments, but after spending more than a few hours on the phone with them and seeing one claim the instructions of another is wrong, I suggest going directly to the source.
2. The restrictions on size of shipping container from the website below (emphasis mine)
§ 173.306 Limited quantities of compressed gases.
4) Gas samples must be transported under the following conditions:
(I) A gas sample may only be transported as non-pressurized gas when its pressure corresponding to ambient atmospheric pressure in the container is not more than 105 kPa absolute (15.22 psia).
(ii) Non-pressurized gases, toxic (or toxic and flammable) must be packed in hermetically sealed glass or metal inner packagings of not more than one L (0.3 gallons) overpacked in a strong outer packaging.
(iii) Non-pressurized gases, flammable must be packed in hermetically sealed glass or metal inner packagings of not more than 5 L (1.3 gallons) and overpacked in a strong outer packaging.
3. The materials which are covered under the restrictions:
§ 173.115 Class 2, Divisions 2.1, 2.2, and 2.3—Definitions.
(a) Division 2.1 (Flammable gas). For the purpose of this subchapter, a flammable gas (Division 2.1) means any material which is a gas at 20 EC (68 EF) or less and 101.3 kPa (14.7 psia) of pressure (a material which has a boiling point of 20 EC (68 EF) or less at 101.3 kPa (14.7 psia)) which—
(1) Is ignitable at 101.3 kPa (14.7 psia) when in a mixture of 13 percent or less by volume with air; or
(2) Has a flammable range at 101.3 kPa (14.7 psia) with air of at least 12 percent regardless of the lower limit. Except for aerosols, the limits specified in paragraphs (a)(1) and (a)(2) of this section shall be determined at 101.3 kPa (14.7 psia) of pressure and a temperature of 20 EC (68 EF) in accordance with the ASTM E681–85, Standard Test Method for Concentration Limits of Flammability of Chemicals or other equivalent method approved by the Associate Administrator. The flammability of aerosols is determined by the tests specified in §173.115 (k) of this section.
The DOT can and does impose severe penalties that includes huge fines and even possible jail time for anyone who knowingly or unknowingly violates these regulations
Now, for the myths associated with these regulations.
1. Since DOT allows 5 liters of flammable sample, all you have to do is only put 5 liters of gas into the 6 liter container to be legal.
This is incorrect, as the gas will expand to the volume of the container and the only change will be in the lower pressure in the container. Since there is only an upper pressure listed, the DOT uses the volume of the container to determine the compliance and not the volume of the gas at the ambient pressures and temperatures.
2. Since the DOT allows 5 liters of flammable sample, all you have to do is add 1 liter of inert gas to a 6 liter container.
This is incorrect, as you now have 6 liters of flammable gas in the container, which is a clear violation of the regulation. The minimal dilution of the addition of 1 liter of inert gas to 5 liters of sample containing ~50% methane only lowers the concentration of methane in the final volume to ~42%, which when the 13% calculation is performed, is still at the upper Flammability range of methane.
3. Since the volume is so small, it is not really a safety threat and the DOT will not enforce such a minor technical violation.
Anything is possible, but when the DOT is prepared to drive a canister from New England to Durham, NC for us to analyze and document the explosive concentration of gas, I sincerely doubt it would be very probable.
So, unless you are shipping a container of a volume of 5 liters or less containing a landfill gas sample there is no way to legally transport it without sufficient dilution with an inert gas such as helium. If the canister is diluted with air, the fixed gas results are skewed by that dilution with compounds of interest. While the dilution concentrations can be removed from the reported concentration, it is more than a little confusing and not as accurate if you do not have an analysis of that dilution gas. To dilute normal landfill gas and maintain a buffer, you will need to fill the canister about 45% of the volume with the inert gas. If you dilute after sampling you will have to stop the sampling at ~433 mmHg in order to pressurize the contents sufficiently to avoid the flammable classification and stay under the 787 mmHg limit set by the DOT. Thus, the easiest method for the field sample is to have the laboratory to pre-charge the canister with inert gas to a level of ~325 mmHg. This means the vacuum in the canister will be 15.5 - 16.5 inches depending on the barometric pressure on site.
If the vacuum is greater than 16.5 and the barometric pressure is 30 inches, you are looking at having a canister which will have to be shipped as containing a flammable gas sample. If it is not 5 liters or less in size DO NOT USE IT or you will not be able to legally do anything with it until you evacuate the sample and replace it with a non-flammable gas.
This also creates issues for the regulatory community as they are tasked with approving protocols, which may in turn violate the laws and reviewing reports, which may have documented such a past violation. Some of the agencies have policies which require the reporting of such violations, which could result in some action by the DOT since all that would be required is the shipping information. The chain-of-custody and the report itself would document who the shipper was and that the regulations were violated in the same manner as a DOT investigation would. At best, it would indicate the possibility of less than 1 liter of sample taken from each sample site, which could invalidate the project. At worst a mistake could result in the specification of an illegal shipping requirement by a regulator.
It also creates issues for quoting projects, especially if the prior testing followed one of the incorrect concepts for compositing. The source being tested really does not have a reason to care as they will not be fined for the shipment and if the sampler is, well that is their problem. If one is quoting against a company who is planning on compositing illegally, there is not much which can be done unless one feels lucky enough to try it too or the protocol is rejected by the regulatory agency. The only consistent way such a problem can be negated is by the regulatory community not accepting such illegal compositing plans, but they have to know and understand the DOT shipping regulations well enough to see the errors in these plans. There is no real way for the shipping company or the DOT to catch the shipment even with warning, unless something specific were to be known about the shipment. There are just too many places from which a shipment could be made over a period of time for this to be probable. Of course, it would only take one such case to ruin a few corporate careers or even shut some doors, so the risk is significant.
As a rule of thumb, if there is any compositing of a ratio greater than 4:1 for landfill samples there should be a level of concern. A ratio of 5:1 in a canister of a volume of 5 liters leaves very little margin for error and no margin for a vacuum in the canister. A 5:1 ratio for a sample diluted sufficiently to not be classified as flammable would require a canister volume of ~9 liters, which is not a common size.
I have discussed these issues with representatives of the DOT and have correspondence on file with them to facilitate shipments, but regulations have changed in the past and may change at some point in the future. At one time we were limited to a 1 liter volume of flammable gas, which has since been changed to the current 5 liters and could possibly be changed again in the future.
If there is any question in your mind on the legality of your shipment, check with the DOT directly, as the liability falls on the shipper to ensure they are meeting all requirements of the regulations. The clients, the regulatory agencies, the laboratories, and even the shipping companies may have information, but that information may not be accurate and final decision is with the shipper.
Triangle Environmental Services, Inc.