Ms. Denise M. Oas — Hazardous Materials Safety Interpretation

Page 1US. Department of Transportation Washingion, DC. 0590 Research and Washington, D.C. special Programs Administration JAN 5 2000 Ms. Denise M. Oas P.O. Box 7377 Reference. No. 98-0347 North Kansas City, MO 64116 Dear Ms. Oas: This is in response to your letter concerning a provision in 49 CFR 173.33(a)(2). This provision restricts a person from loading or accepting different materials on the same multi-unit cargo tank motor vehicle if, as a result of any mixture of the materials, an unsate condition would occur such as an explosion, fire, excessive increase in pressure or inconvenience it may have caused. heat, or the release of toxic vapors. I apologize for the delay in responding and regret any In your letter, you referred to a statement published in the June 17, 1991 Federal Register publication in which we stated that the restriction in § 173.33(a)(2) was not intended to prevent ine shipment of materals that, if mixed, would produce a moderate exothermic reaction that would not start a fire, rupture the tank or release acutely toxic vapors. You asked if this interpretation is correct and if, not, just how much of an increase in pressure or heat is permitted before creating a violation of this section. The above interpretation is correct. In addition to meeting the provision in § 173.33(a)(2), cargo tanks must meet the general requirements for all bulk packagings in limited, and closed, so that under conditions that normally occur in transportation: 1) there will be no identifiable release of hazardous materials to the environment; 2) the effectiveness of the packaging will not be substantially reduced; and 3) there will be no mixture of gases or vapors in the package which could through any credible spontaneous Many factors affect how materials may react with each other. They include the chemical composition and properties of the materials involved, and how they react to air, water, contaminants, or temperature conditions during transportation. Because there are so many variables, under the Hazardous Materials Regulations, the parties involved must evaluate the potential risk posed by different materials that are offered and accepted for transportation on the same multi-tank cargo tank motor vehicle. If your client has 173.33 980347#

Page 2- specific questions on making these determination, your client may contact Mr. Charles Hochman, Office of Hazardous Materials Technology, at (202) 366-4545 for assistance. I hope this satisfies your request. Sincerely, itatte 2. Michell Hattie L. Mitchell, Chief Regulatory Review and Reinvention Office of Hazardous Materials Standards#

Page 398-0347 DENISE M. OAS P.O. BOX 7377 mack NORTH KANSAS CITY. MISSOURI 64116 $173.33 (816) 455-7300 November 12, 1998 Mr. Edward T. Mazzullo - DHM -10 Director, Office of Hazardous Materials Standards, RSPA 400 Seventh Street, Southwest U.S. Department of Transportation Room 8100 Washington, DC 20590 Dear Mr. Mazzullo, A client of mine has asked for an interpretation from your office regarding 49 C.F.R. 173.33(a)(2) which provides that: Two or more materials may not be loaded or accepted for ray sportatio it t matemes, ago tank motor tich ve if occur, suh as nv mixture ot the material: an explosion, fire, excessive increase in pressure or heat, or the release of toxic vapors. A statement published in the Federal Register in 1991 noted that the intent of the section is to prevent shipment of materials that, if mixed, would cause a fire, a tank rupture or the release of acutely toxic vapors. 56 Fed. Reg. 27872 June 17, 1991). It further noted that the section was not intended to prevent the shipment of materials that, if mixed, would produce a moderate exothermic reaction that would not start a fire, rupture the tank or release acutely toxic vapors. pressure or heat that is prohibited is an increase sufficient to cause a fire, tank Thank you for your assistance. Very Truly Yours, Deni Eas Deni Oas#