Verifying presence of odorant protects customers, marketers

December 12, 2011 By    

A common issue that can create a basis for liability in defending gas explosion cases is the level of odorant in the gas as it is emitted into the atmosphere. When people who are injured in a gas explosion testify that they did not smell gas, the focus immediately turns to the odorant in the gas.

In accidents that include personal injuries, it is standard to obtain a liquid sample of gas to be lab tested to determine the level of odorant in the gas.

NFPA 58 references that 1 pound of ethyl mercaptan per 10,000 gallons of propane has been shown to be an effective odorant. The code requires the odorant to be detectible at one-fifth the lower explosive limit. The amount of ethyl mercaptan required in propane exceeds the amount of odorant needed to meet this threshold requirement. The general industry practice is to place 1.5 pounds of ethyl mercaptan per 10,000 gallons of propane. This level is substantially above the threshold requirement to meet the code standard.

In tests following an accident, there are occasions when the level of odorant found in the liquid sample falls below 1 pound per 10,000 gallons. This can occur in two ways: The odorant was not added in the right quantities at the outset or the odorant was lost due to several possible events after it was added to the propane.

The safeguards present for making sure odorant is added in sufficient quantities at the outset vary at the terminals where the propane is picked up. Mechanical devices are designed to inject the odorant at the right levels before it leaves the terminal. The level of odorant injected is then documented on a bill of lading that goes with the product until it reaches the local propane marketer. This is the only documentation showing the amount of odorant actually in the propane.

A sniff test required by the code is the other documentation of odorant. This takes place when LP gas is delivered to a bulk plant and when shipments of LP gas bypass the bulk plant. In many instances, the local propane marketer does not transfer propane to the bulk plant. An independent transport driver often does this. The bill of lading is often viewed as the written documentation that the propane has been sniff tested at the point of transfer to the bulk plant or when the bulk plant is bypassed. A sniff test does not confirm the level of odorant in the propane – just that it can be detected by smell.

So there are two pieces of evidence that can be used to defend claims of insufficient odorant against propane marketers: a bill of lading showing odorant levels that meet code requirements and a documented sniff test by a bill of lading or otherwise that meets the requirements of the code.

Odorant loss can also occur in new tanks or cylinders. That is why there is a general requirement that the first fill be to 80 percent. This does not eliminate odorant loss in the container but reduces its effect. Odorant loss can also occur in older containers through oxidation in the container degrading the odorant. There are myriad ways odorant can be lost outside the container as well. Leeching in the ground, absorption, adsorption and masking are just some examples.

It is important from a safety point of view that odorant levels and sniff testing are properly documented. It is also important to follow safe procedures when installing new containers to reduce the chance of odor fade. And it is helpful to identify the ways that odorant can be lost in the environment, recognizing that possibility when called about a potential gas leak.

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