Health & Safety Insights

OSHA’s Process Safety Management (or PSM) standard at 29 CFR 1910.119 is intended to prevent or minimize the consequences of catastrophic releases of toxic, reactive, flammable, or explosive chemicals. This includes certain flammable liquids, so it’s important to know when the PSM standard kicks in for them. Specifically, a process may be subject to the standard when it:

• Involves a flammable liquid with a flashpoint below 100°F,
• Is onsite in one location, and
• Is in a quantity of 10,000 pounds or more.

These provisions at 1910.119(a)(1)(ii) are only the starting point for an applicability determination. As discussed below, several exemptions affect PSM coverage.

What counts as a process?

According to paragraph (b) of the standard, a “process” means any activity involving a highly hazardous chemical (HHC) including any use, storage, manufacturing, handling, or onsite movement of such chemicals, or any combination of these activities. OSHA’s definition goes on to say that a single process includes:

• Any group of interconnected vessels, or
• Separate vessels located so that an HHC could be involved in a potential release.

As a result, facilities need to aggregate quantities in interconnected or co-located vessels to assess whether the threshold quantity (or TQ) is met.

What does “onsite in one location” mean?

OSHA interprets the term onsite in one location to mean that a TQ of an HHC exists within contiguous areas (meaning nearby or in actual contact) under the control of an employer or affiliated employers. In addition, the HHC is contained either in interconnected vessels or co-located vessels close enough that they could be involved in a potential catastrophic release.

That said, trucks and pipelines outside the boundaries of the employer's property, which may be regulated by the Department of Transportation in any event, are excluded from the scope of the standard. That’s because OSHA has explained in a June 7, 2007, interpretation in the Federal Register that the term onsite in one location serves to exclude from PSM coverage any situation where the HHC threshold could only be met if all amounts in interconnected or proximate vessels or pipes were aggregated but some of the amounts needed to meet that TQ are outside the perimeter of the employer's facility.

How are flammable liquid quantities determined?

In evaluating whether a TQ or greater amount exists at any one point in time, flammable liquids contained in a process are considered in the aggregate. From this standpoint, flammable liquids and flammable gases are treated separately.

If a mixture meets the applicability criteria for a flammable liquid under 1910.119(a)(1)(ii), the mixture quantity is used to figure out whether a TQ exists. OSHA directive CPL 02-01-065 describes a mixture consisting of:

• 2,000 pounds of fine, non-soluble, non-combustible solid, and
• 8,000 pounds of a flammable liquid that is contained in a process.

In that example, the mixture has a flashpoint of less than 100°F, which meets the definition of a flammable liquid, and a TQ exists in that process. Therefore, the total amount of flammable liquid is 10,000 pounds, even if some component(s) of the mixture alone would not meet the required flashpoint.

What about the atmospheric tank exemption?

An “atmospheric tank” is a storage tank designed to operate at pressures from atmospheric through 0.5 pounds per square inch gauge (psig). See paragraph (b) of the standard. This term matters because flammable liquids are not counted if they:

• Have a flashpoint below 100°F, and
• Are stored in or transferred to atmospheric tanks, and
• Are kept below their normal boiling point without benefit of chilling or refrigeration.

When all three conditions are met as specified in 1910.119(a)(1)(ii)(B), the particular flammable liquid is not used to determine whether a process contains a TQ. This exception also comes into play for flammable liquids stored in small atmospheric containers or 55-gallon drums, provided that the same three criteria are satisfied, even when the quantity exceeds 10,000 pounds. Yet, such flammable liquid storage must meet OSHA’s Flammable Liquids standard at 1910.106.

Note that the exception is limited to storage and transfer. If a different process activity occurs, the flammable liquids are not exempt from counting toward the TQ. For instance, when an atmospheric tank is used to manufacture a finished product through mixing and blending, the exception falls away.

Likewise, tanks that operate at pressures exceeding 0.5 psig are not atmospheric tanks, so storage of a TQ of flammable liquids in those tanks is a PSM-covered process.

Be aware that storing flammable liquid with the benefit of chilling or refrigeration would not negate the atmospheric storage exemption when the liquid is not required to be refrigerated to keep it below its normal boiling point. One such situation is when an employer elects to refrigerate a chemical for quality control purposes. However, if it was documented that the employer must use chilling or refrigeration to keep the flammable liquid below its normal boiling point, then the exemption at subparagraph (a)(1)(ii)(B) would not apply.

What about other exemptions?

Other carve-outs are listed in 1910.119(a). The PSM standard does not extend to:

• Retail facilities;
• Oil or gas well drilling or servicing operations;
• Normally unoccupied remote facilities; or
• A process which involves a Category 1 flammable gas or a flammable liquid with a flashpoint below 100°F onsite in one location, in a quantity of 10,000 pounds or more, where the flammable gas or liquid is a hydrocarbon fuel used solely for workplace consumption as a fuel, if the fuel is not a part of a process containing another HHC covered by the standard.

OSHA CPL 02-01-065 provides the agency’s technical interpretation of these exemptions.

Can a facility reduce inventory to avoid PSM?

The short answer is yes. A facility that brings inventories down below the PSM TQ may find that its processes are no longer subject to the PSM standard. Possible strategies include improving inventory control or accepting smaller deliveries. When reduced inventory is not feasible, the employer might consider dispersing inventory among several onsite locations so that any release in one location will not cause a release in another. OSHA notes that lowering and dispersing inventories may also lessen the consequences of a catastrophic incident.

At the same time, OSHA says reducing inventories below PSM TQs does not relieve employers of their duty under the Occupational Safety and Health Act to provide safe and healthful working conditions for their employees. Chemical hazards may still be present, and, in the case of flammable liquids, other standards may continue to govern, such as:

• OSHA standards like 1910.106, Flammable Liquids, and 1910.1200, Hazard Communication.
• EPA standards like 40 CFR 68, Chemical Accident Prevention Provisions, also known as the Risk Management Program (RMP) rule. OSHA PSM excludes some processes that EPA RMP does not, and vice versa.
• Other state and local building and fire codes, which may incorporate industry standards like the International Building Code (IBC), International Fire Code (IFC), and National Fire Protection Association (NFPA) 30.

Key to remember

One way the OSHA PSM standard is triggered is when a process involves 10,000 pounds or more of a flammable liquid with a flashpoint below 100°F onsite in one location. Facilities need to consider interconnected or co-located vessels and review the atmospheric tank and other exemptions. Even when a facility is off the hook from PSM, other OSHA, EPA, state, and local standards and codes may still govern flammable liquid storage and handling.