# Betts Industries, Inc. — Hazardous Materials Safety Interpretation **Citation:** 22-0011 **Type / status:** guidance / guidance **Agency:** Pipeline and Hazardous Materials Safety Administration **Effective:** Not stated **Published:** 2022-07-28 22-0011 response to Betts Industries, Inc. concerning 178.345. ## Document text <<>> 1200 New Jersey Avenue, SE Washington, DC 20590 U.S. Department of Transportation Pipeline and Hazardous Materials Safety Administration July 28, 2022 Mr. David J. Adams Director of Design Engineering Betts Industries, Inc. 1800 Pennsylvania Ave W. Warren, PA 16365 Reference No. 22-0011 Dear Mr. Adams: This letter is in response to your February 23, 2022, email requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to the venting capacity of pressure relief systems for cargo tanks, specified in § 178.345-10(e). You state that “Table 1 - Minimum Emergency Vent Capacity” in paragraph (e) includes a note which allows for interpolation of the values on the table for intermediate sizes of cargo tanks, specifically exposed area in square feet. However, you note that it is not stated whether one can extrapolate the data on the table for cargo tanks larger than 1,000 square feet. You have provided an additional table showing data that you have interpolated and extrapolated from Table 1 in § 178.345-10(e). Lastly, you state that you are not aware of any regulation which limits the size of a cargo tank to less than 1,000 square feet of exposed area. We have paraphrased and answered your questions as follows: Q1. You ask whether there is any regulation that limits the size of a cargo tank to being no greater than 1,000 square feet of exposed area. A1. Although the HMR do not limit the size of a cargo tank, the Federal Highway Administration (FHWA) regulates commercial vehicle weight and size requirements, in conjunction with state enforcement agencies. More information on the federal commercial vehicle size and weight program can be found on FHWA’s website at the following web address: https://ops.fhwa.dot.gov/freight/sw/overview/index.htm. Q2. You ask what venting capacity is required if the cargo tank has an exposed area of greater than 1,000 square feet. <<>> A2. As you have stated in your email, the table for minimum emergency vent capacity in § 178.345-10(e) does not have a corresponding value for cargo tanks with an exposed area of greater than 1,000 square feet. It is the opinion of this Office that for cargo tanks with greater than 1,000 square feet of exposed area, extrapolation would be acceptable to determine the value of the cubic feet free air per hour. However, the extrapolation calculation should be verified by the Design Certifying Engineer responsible for determining compliance of the cargo tank design. Q3. You ask whether extrapolation of the data from Table 1 in § 178.345-10(e) is permitted. A3. Please see answer A2. I hope this information is helpful. Please contact us if we can be of further assistance. Sincerely, T. Glenn Foster Chief, Regulatory Review and Reinvention Branch Standards and Rulemaking Division <<>> Larson 22-0011 From: Raynor, T"Mia (PHMSA) To: Hazmat Interps Subject: FW: Request for Interpretation 49CFR§178.345-10 Date: Wednesday, February 23, 2022 1:49:20 PM Attachments: image003.png Good Afternoon, Would someone be able to assist the user below? Thanks, T’Mia Raynor Webmaster, Office of the PHMSA CIO US Department of Transportation Pipeline and Hazardous Materials Safety Administration 1200 New Jersey Ave. SE, Washington, D.C., 20590 Office: 202.366.9818 ◊ Mobile: 202.580.9447 PHMSA Home | LinkedIn | Twitter | HAZMAT | OPS From: David J. Adams Sent: Wednesday, February 23, 2022 12:54 PM To: PHMSA Website Manager Subject: Request for Interpretation 49CFR§178.345-10 CAUTION: This email originated from outside of the Department of Transportation (DOT). Do not click on links or open attachments unless you recognize the sender and know the content is safe. To Whom It May Concern, I would like to request a regulation interpretation or clarification. Current regulation reads: 49 CFR 178.345 10(e) Venting capacity of pressure relief systems. The pressure relief system (primary and secondary, including piping) must have sufficient venting capacity to limit the cargo tank internal pressure to not more than the cargo tank test pressure. The total venting capacity, rated at not more than the cargo tank test pressure, must be at least that specified in table I, except as provided in § 178.348-4. Table I - Minimum Emergency Vent Capacity [In cubic feet free air/hour at 60 °F and 1 atm.] Exposed area in square feet Cubic feet free air per hour 20 15,800 30 23,700 40 31,600 50 39,500 <<>> 60 47,400 70 55,300 80 63,300 90 71,200 100 79,100 120 94,900 140 110,700 160 126,500 180 142,300 200 158,100 225 191,300 250 203,100 275 214,300 300 225,100 350 245,700 400 265,000 450 283,200 500 300,600 550 317,300 600 333,300 650 348,800 700 363,700 750 378,200 800 392,200 850 405,900 900 419,300 950 432,300 1,000 445,000 This table includes note 1 which allows for interpolation for intermediate sizes but it does not mention if extrapolation is permitted for larger size cargo tanks. I am not aware of any regulation which limits the size of a cargo tank to under 1,000 square feet of exposed area. The specific questions are: 1. Is there any regulation limiting the size of a cargo tank (specially a specification DOT406) to no greater than 1,000 square feet of exposed area? 2. 3. What venting capacity is required if the cargo tank has exposed area greater than 1,000 square feet? Is extrapolation of Table 1 permitted? (An example of extrapolated data is provided in Appendix A.) Note 1: Interpolate for intermediate sizes. Appendix A – Example of extrapolated capacity curve based off Table 1 of 49 CFR 178.345 10. <<>> Exposed Area (sq. ft.) Req. Vent Capacity (scfh) Exposed Area (sq. ft.) Req. Vent Capacity (scfh) 20 15,800 450 283,200 40 31,600 475 291,900 80 63,300 500 300,600 100 79,100 525 308,950 120 94,900 550 317,300 140 110,700 575 325,300 160 126,500 600 333,300 180 142,300 625 341,050 200 158,100 650 348,800 225 191,300 675 356,250 250 203,100 700 363,700 275 214,300 725 370,950 300 225,100 750 378,200 325 235,400 775 385,200 350 245,700 800 392,200 375 255,350 825 399,050 400 265,000 850 405,900 425 274,100 875 412,600 Thank you for your time and consideration. Exposed Area (sq. ft.) Req. Vent Capacity (scfh) 900 419,300 925 425,800 950 432,300 975 438,650 1000 445,000 Exposed Area Extrap. Cap. 1,025 451,275 1,050 457,550 1,075 463,700 1,100 469,850 1,125 475,900 1,150 481,950 1,175 487,900 1,200 493,850 1,225 499,725 1,250 505,600 1,275 511,375 1,300 517,150 <<>> Best regards, David J. Adams Director of Design Engineering dadams@bettsind.com P 814-723-1250 Ex. 136 | F 814-723-5513 Betts Industries, Inc. 1800 Pennsylvania Ave W., Warren, PA 16365 confidential information. Unless stated to the contrary, any opinions or comments are personal to the writer and do not represent the **** Betts Industries, Inc. Email Notification **** This e-mail is only intended for the person(s) to whom it is addressed and may contain official view of the company. If you have received this e-mail in error, please notify us immediately by reply e-mail and then delete this message from your system. Please do not copy it or use it for any purposes, or disclose its contents to any other person. Thank you for your ## Provenance - Official: Yes - Source: - Source ID: `phmsa` - SHA-256: `d842313b775f0f86a2aa161fb2db4dd089db3da098d8533211d9931d842fcdf6` - Retrieved: 2026-08-20T00:59:31.977Z - Exported: 2026-08-22T04:03:58.075Z - Document slug: `phmsa-interpretation-22-0011` ### Source metadata ```json { "materialSubtype": "interpretation", "interpretationArea": "hazardous_materials", "representation": "full_text_from_official_pdf", "companies": [ "Betts Industries, Inc." ], "individuals": [ "David J. 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