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.

January 26, 1994

Mr. Rashid Hamsayeh, C.S.P.
Corporate Safety Specialist
Formosa Plastic Corporation, USA
9 Peach Tree Hill Road
Livingston, New Jersey 07039

Dear Mr. Hamsayeh:

This is in response to your letter of October 29, and to the November 18, telephone conversation with Mr. James C. Dillard of my staff, in which you requested of the Occupational Safety and Health Administration (OSHA) an interpretation of whether the requirements of 29 CFR 1910.119, Process safety management of highly hazardous chemicals apply to "Dowtherm". In your letter, you stated the following:

Instead of steam, Dowtherm is used as a heating medium. Unlike steam, this liquid is heated to approximately 600 Degrees F. and operated at a low pressure of 30 psig. At ambient pressure and temperature, Dowtherm is not flammable because it has a flashpoint of approximately 400 Degrees F.

For defining flammable liquids under 1910.119, we refer to 1910.1200(c), Hazard communication standard, which is quoted, as follows:

Flammable liquid means any liquid having a flashpoint below 100 Degrees F.(37.8 C.), except any mixture having components with flashpoints of 100 Degrees F. (37.8 C.) or higher, the total of which make up 99 percent or more of the total volume of the mixture.

As you may be aware, OSHA requires that combustible liquids heated for use to within 30 Degrees F. (16.7 C.) of their flashpoints be handled in accordance with the requirements for the next lower class of liquids. This is covered at 1910.106(a)(18)(iii) as follows:

When a combustible liquid is heated for use to within 30 Degrees F. (16.7 C.) of its flashpoint, it shall be handled in accordance with the requirements for the next lower class of liquids.

However, according to the specifications you gave us, Dowtherm is a Class IIIB liquid, as defined at 1910.106(a)(18)(ii)(b) as follows:

Class IIIB liquids shall include those with flashpoints at or above 200 Degrees F.(93.3 C.). This section does not cover Class IIIB liquids. Where the term "Class IIIB" liquids is used in this section, it shall mean only Class IIIA liquids.

As a result of the definitions in 1910.106 and .1200 as quoted above, and the specification you have provided, we conclude that Dowtherm is not intended to be covered by 1910.119.

If you have any additional questions, please feel free to contact Mr. James C. Dillard of my staff, at (202) 219-8031.


Raymond E. Donnelly, Director
Office of General Industry
Compliance Assistance