“On the first day of school, you got to be real careful where you sit. You walk into the classroom and just plunk your stuff down on any old desk, and the next thing you know the teacher is saying, ‘I hope you all like where you’re sitting, because these are your permanent seats.’”  — Jeff Kinney

I once worked with a client that had very carefully redesigned one of their processes to keep the one listed compound below the threshold quantity (TQ) so that the process would not be covered under the Process Safety Management (PSM) Standard, 29 CFR 1910.119. The process was able to operate using only one drum at a time. They were quite pleased.

The listed compound was formaldehyde, which has a PSM TQ of 1,000 lbs.  They were buying it as formalin, a 37% solution of formaldehyde in water, stabilized with 10% methanol.  A 55-gallon drum can hold 373 lbs. of formalin.  At 37%, a drum will only contain 138 lbs. of formaldehyde.  138 lbs. of formaldehyde vs. a TQ of 1,000 lbs. Great!

“So, do you only buy one drum at a time?” No, they went through one or two drums per week, so they bought enough to last for a couple of months—12 drums, three pallets with four drums per pallet. A total of 1,656 lbs of contained formaldehyde at a time. They stored the drums in the raw materials warehouse, out of the weather.

“Well, good job on eliminating the manufacturing process under the TQ so it’s not a covered process, but your warehouse still is.”

Are You Kidding?

No, not kidding. Warehouses can be covered processes. “But we don’t process anything in the warehouse. Does PSM even apply?”

It’s important to remember that what OSHA means by “process” isn’t what most process engineers mean by “process”. Most of us think of a process as a unit operation or a series of unit operations that transform raw materials into intermediates or finished products. That is not how OSHA defines a process:

Process means any activity involving a highly hazardous chemical including any use, storage, manufacturing, handling, or the on-site movement of such chemicals, or combination of these activities. For purposes of this definition, any group of vessels which are interconnected and separate vessels which are located such that a highly hazardous chemical could be involved in a potential release shall be considered a single process.

A process is “any activity” and includes storage. Moreover, a group of separate vessels “shall be considered a single process.” So, the formalin drums are sitting together on three pallets in the warehouse. What vessels are in the warehouse?

The drums are the vessels.

Flammable Storage

OSHA only lists 137 toxic chemicals. However, any flammable liquid with a flashpoint less than 100°F is also defined as a highly hazardous chemical (HHC) by the PSM standard, as is any Category 1 flammable gas. The TQ for any flammable HHC is 10,000 lbs. With a typical specific gravity of around 0.8, that means that a 55-gallon drum holds about 370 lbs., and 27 drums can be enough to exceed the TQ.

Fortunately for those enterprises trying to avoid having a covered process, there is the atmospheric storage exception: Flammable liquids “stored in atmospheric tanks or transferred which are kept below their normal boiling point without benefit of chilling or refrigeration” are excepted from the PSM standard. OSHA considers drums to be atmospheric tanks.

This exception only applies to flammable liquids. It does not apply to any of the 137 listed toxics. It does not apply to flammable gases, which cannot be stored in atmospheric tanks and are not liquids.

This exception only applies to storage in atmospheric tanks. Atmospheric tanks can include drums, pails, totes, and jugs that are not pressurized. They include whiskey barrels. (The flash point of 80 proof alcohol is 79°F, so whiskey is certainly a flammable liquid covered by the PSM standard.)

The atmospheric tank exception does not apply to pressurized containers, like aerosol cans or pressurized drums. What is an atmospheric tank? It’s a storage tank designed to operate at a pressure between atmospheric pressure and 0.5 psig. If there is a nitrogen blanket on that drum, it needs to be no more than 0.5 psig (13.85 inches of water). Otherwise, that container is not an atmospheric tank. If the container is designed to operate under vacuum, it is not an atmospheric tank.

What About RMP?

OSHA is not the only federal agency with regulations about process safety. After the PSM standard came out, the EPA issued its own regulations. Commonly known as the Risk Management Planning (RMP) rule, 40 CFR 68, the EPA regulations differ from the OSHA regulations in some important ways.

To start with, their list of toxics is much shorter than OSHA’s list. There are only 77 toxics on the RMP list, and there is only some overlap. Even where there is overlap, the TQs for the two standards are often different; a TQ on the RMP list is usually higher than the TQ on the PSM list if the chemical appears on both.  For instance, OSHA lists formaldehyde (but only if the concentration is 37% or higher) with a TQ of 500 lbs. contained formaldehyde, while the EPA lists formaldehyde (if the solution is a concentration is higher than 1%), but the TQ of the contained formaldehyde is 15,000 lbs. So, my client’s warehouse was covered under PSM but not under RMP.

Likewise, the EPA doesn’t cover all flammable liquids and Category 1 flammable gases. Instead, it has a list of 63 flammables that are covered. That means that the vast majority of flammable liquids are not covered under RMP. If a flammable liquid is on the EPA list, then 10,000 lbs. or more stored together is a covered process. Even if they are in drums. When the EPA issued its regulation, it didn’t like the atmospheric exemption, so it deliberately left it out of the RMP rule.

What to Do?

The reason that three pallets of formalin drums stored together in a warehouse are a covered process is not because any one drum exceeds the TQ, but because in aggregate, the 12 drums exceed the TQ. The first thing to consider is reducing the quantity of HHCs in storage. Twelve drums of formalin contain a total of 1,656 lbs of contained formaldehyde, more than the TQ. Even eight drums of formalin contain a total of 1,104 lbs of contained formaldehyde, still more than the TQ of 1,000 lbs. But one pallet is less than the TQ. Even the amount contained in seven drums is less than the TQ.

What if reducing the quantity to less than the TQ isn’t practical? Then another option is to split it up. Remember, a group of drums is considered a single process when they are “located such that a highly hazardous chemical could be involved in a potential release”. If they are stored separately, say in separate warehouses or in different sections of a single warehouse separated from each other by fire walls and protected with fire suppression, then they are not a single process.

My client? First, they reduced the quantity in storage from 12 drums to 8 drums. Then, they stored one pallet in their raw material warehouse and one pallet in their finished goods warehouse.

Keep in mind, the TQ applies to the maximum quantity, not the average quantity.

The Next Thing You Know

The operators of some covered processes have trouble reconciling their personal definition of “process” with the regulatory definition of “process”. Even when they get past that, they think of “storage” as something that happens in tank farms. Then the next thing they know, they are realizing that their warehouses are covered processes under the standards.

If you are using or producing listed HHCs, it’s hard to imagine that you are not storing them as well. Is your warehouse storage a covered process? You should check. If it is, then make sure that this “process” complies with all the elements of the standards.