OSHA requirements are set by statute, standards and regulations. Our interpretation letters explain these requirements and how they apply to particular circumstances, but they cannot create additional employer obligations. This letter constitutes OSHA's interpretation of the requirements discussed. Note that our enforcement guidance may be affected by changes to OSHA rules. Also, from time to time we update our guidance in response to new information. To keep apprised of such developments, you can consult OSHA's website at https://www.osha.gov.

June 22, 1994

Mr. Thomas J. Lukish
James River Corporation
P.O. Box 2218
Richmond, Virginia 23217

Dear Mr. Lukish:

This is in response to your January 31 letter, requesting interpretation of the Process Safety Management (PSM) of Highly Hazardous Chemicals standard, 29 CFR 1910.119. Specifically, you requested clarification as to whether processes used in the pulp and paper industry are covered by the PSM standard because the processes contain chlorine dioxide (ClO(2)). Please accept our apology for the delay in responding.

Enclosed with your letter are block diagrams of two processes containing chlorine dioxide. Your supporting calculations on these block diagrams show that each process has an operating capacity of approximately 100 pounds (45.359 kg), of ClO(2) gas, exclusive of ClO(2) in the water solutions in the storage tanks. Based on the information provided on the block diagrams, the amount of ClO(2) in the water solution stored in each process is approximately 760 pounds (344.73 kg). The calculated total amount of ClO(2) contained in each process is approximately 860 pounds (390.09 kg), which is less than the threshold quantity of 1000 pounds (453.59 kg) and would not be covered by the PSM standard. One tenth of one percent ClO(2) by weight was used to calculate the amount of ClO(2) in the water solutions. It is noted that the storage tanks in each process have the capacity to hold, collectively, ClO(2) water solutions which could contain 1000 pounds or more of ClO(2).

An artificial atmosphere must be provided to maintain the ClO(2) in the water solution. Furthermore, when the ClO(2) in water solution is subjected to atmospheric conditions, which could result from a process containment breach, there could be a catastrophic release of the ClO(2) water solution from the storage tanks. Employees could be exposed not only to the gaseous ClO(2) but also, to the ClO(2) which would disassociate readily from the water solution. As such, both the ClO(2) in water solution and freestanding ClO(2) gas must be considered when determining whether there is a threshold quantity or greater amount of ClO(2) at any particular time in each of your processes.

If you intend to operate the aforementioned processes to avoid being subject to the PSM standard, you must have an effective program (and be prepared to demonstrate to OSHA) that these processes are operated to preclude an otherwise covered amount of ClO(2) from being in these processes at any particular time. Also, we recommend you carefully consider the definition of "process" to determine further possible applicability of the PSM standard. Other covered processes, for example, a process containing a threshold or greater amount of a flammable liquid, such as, methanol (noted on one of your block diagrams) may be interconnected with the processes containing ClO(2).

We appreciate your interest in occupational safety and health. If we can be of further assistance, place do not hesitate to contact us.


John B. Miles, Jr., Director
Directorate of Compliance Programs