Wednesday, June 10, 2015

Change in PSM Concentration Interpretations

While I spend a great deal of time looking at a wide variety of chemical safety and security web sites for changes in government policies and procedures, I cannot claim to comprehensively cover the topic. Fortunately, I have a large number of readers that run across things from time-to-time that I may have missed and feel free to point me in the right direction. This happened today with two new PSM interpretive documents that have been posted to the OSHA web site:

Unfortunately OSHA does not date its web pages (or changes to them) and these were not posted as .PDF documents, just ephemeral html pages, so it is going to be hard to intelligently reference these pages (or potential changes to them), but it does seem that they were posted to the web on Monday, June 8th, 2015. Today I’ll take a quick look at the first one and I’ll deal with the RAGAGEP interpretation at some later date.


The OSHA Process Safety Management Standard (29 CFR 1910.119) requires manufacturers to put in place a process safety management (PSM) program any time that they have at least a minimum amount of a highly hazardous chemical involved in a manufacturing process. Appendix A to the standard lists the highly hazardous chemicals that could trigger the PSM requirement and the minimum amount (threshold quantity – TQ) that actually triggers the requirement.

Generally speaking, manufacturers do not use chemically pure elements or compounds in their processes and some chemicals come dissolved in solvents and yet others come in mixtures with multiple other chemicals. All of this can make it somewhat difficult to determine how much of a specific chemical exists in the process. To make things even more complicated, almost all hazardous chemicals have some concentration below which they are not extremely hazardous, so they should not require the establishment of a PSM program below those concentrations.

The PSM standard attempts to address this issue by listing (for some chemicals) minimum concentrations that must be exceeded for the PSM standard to apply. Ammonia solutions, for instance are not regulated under the PSM standards at concentrations below 44%. Unfortunately, most of the chemicals listed in Appendix A do not have a minimum concentration listed.

Shortly after the Standard was published in 1992 OSHA was forced to clarity the concentration issue with a series of letters of interpretation and compliance directives on this subject. Letters through 1994 finally settled on a somewhat ambiguous concentration process that centered on the ‘maximum commercial grade concentration’. Even so the interpreted standard was vague on whether or not process concentrations below the MCGC could trigger the PSM program requirements or even whether the TQ was determined by just the amount of the listed chemical in the solution or the entire solution.

The general rule that I have heard over the years in industry has been that we would only count the total amount of the actual listed chemical to determine TQ. We would determine what the highest concentration of the material was in our process and if it was at or above the listed concentration in Appendix A or, if not listed, the MCGC that we could find from suppliers, then we would calculate the maximum quantity in our process.

OSHA Review

Because of requirements of President Obama’s Chemical Safety and Security Executive Order (EO 13650) to re-look at PSM and RMP (the EPA’s similar Risk Management Program) OSHA conducted a review of the PSM program to include the concentration/TQ issues. This review was included as part of the Request for Information (RFI) that OSHA published in December 2013.

In that RFI OSHA asked if it should use the 1% concentration rule used by EPA for their RMP program. Essentially the EPA says that any time there is more than 1% of a chemical in a process or mixture it must be counted to determine if the process should be covered and the amount counted will be determined by multiplying the concentration by the amount of the material in the process. Three is a way to avoid this rule if the process owner can demonstrate that at the concentration found in the process the partial pressure of the chemical in the headspace above the process is less than 10 mmHg.

There were a large number of public responses received on that RFI. I reviewed those responses in a series of blog posts last year. I did not note any real substantial responses to the concentration rule questions in those responses.

New OSHA PSM Interpretation

According to the OSHA web site, OSHA has essentially adopted the EPA concentration rule:

“In determining whether a process involves a chemical (whether pure or in a mixture) at or above the specified threshold quantities listed in Appendix A, the employer shall calculate:
(a) the total weight of any chemical in the process at a concentration that meets or exceeds the concentration listed for that chemical in Appendix A,  and
(b) with respect to chemicals for which no concentration is specified in Appendix A, the total weight of the chemical in the process at a concentration of one percent or greater.  However, the employer need not include the weight of such chemicals in any portion of the process in which the partial pressure of the chemical in the vapor space under handling or storage conditions is less than 10 millimeters of mercury (mm Hg).  The employer shall document this partial pressure determination.

OSHA has also clarified that in determining the TQ only the weight of the actual listed chemical will be considered.


In many ways I really think that the new OSHA interpretation makes a lot of sense. Aligning the concentration rule with the EPA’s RMP program will, in the long run, eliminate a lot of confusion that exists between the two programs.

I am not sure, however, that either program can really justify that they identify hazardous mixtures that could harm either facility employees (the goal of the PSM program) or facility neighbors (the goal of the RMP program) if they were released from the process. Short of actually measuring the hazard (relatively easy for flammable hazards, very complicated and expensive for toxic hazards and somewhere in between for corrosive hazards) I suppose that this is a reasonable method of estimating process hazards. Process owners should, in my opinion, be given an option to prove that the concentration in their process is safe as a method to opt out of either the PSM or RMP programs.

I am very concerned, however, that a major change has been made to a major regulatory program without adequately involving the regulated and affected communities involved in the change. I understand that there has not actually been a change in the wording of §1910.119. Technically this may mean that there has not been a change to the regulation that needed to go through the publish and comment process. But there has been a significant change made to the regulatory process.

I suspect that there are a very large number of chemical processes that were not ‘covered’ under the old MCGC interpretation that now will be covered under the 1% interpretation. Bringing these process may (or may not) be a process safety improvement (probably will be in most cases in my opinion), but it is certainly a major increases in regulatory coverage; an increase made by administrative fiat.

There has certainly been no attempt by OSHA to estimate the cost of this change or justify that cost by estimates of safety improvement. In my not so humble opinion, until that risk benefit calculation is publicly made, OSHA cannot go through with this program change.

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