May 8, 2025

Mr. Luis Balderas
Nippon Chemical Texas Incorporated (NCTI)
10500 Bay Area Blvd,
Pasadena, TX 77507
lbalderas@nctius.com

Dear Mr. Balderas:

Thank you for your inquiry to the Occupational Safety and Health Administration (OSHA). Your emailed inquiry was forwarded to the Directorate of Enforcement Programs. You requested information regarding OSHA's Benzene and 1,3-Butadiene standards at 29 CFR § 1910.1028 and 29 CFR § 1910.1051, respectively. This letter constitutes OSHA's interpretation only of the requirements discussed and may not be applicable to any questions not delineated within your original correspondence. Your questions are presented below, followed by OSHA's responses.

Background: Your emailed inquiry stated that the Benzene and 1,3-Butadiene (Butadiene) standards require employers to institute engineering controls and work practices to reduce and maintain employee exposures to or below the permissible exposure limits (PELs), except to the extent that the employer can establish that controls are not feasible. You also stated that according to the National Institute for Occupational Safety and Health, engineering controls remove hazardous conditions by placing a barrier between the worker and the hazard.

Question 1: Would the installation of bellow valves, leak-proof, or double-seal valves be considered forms of engineering controls?

Response: Yes, under the Benzene and Butadiene standards, bellow valves, leak-proof and double seal valves would be considered forms of engineering controls. These two standards are generally performance-oriented; employers may implement a combination of engineering controls and work practices suited to their particular facilities to comply with the standards' provisions, including their requirements to reduce and maintain employee exposure at or below the PELs. The preamble to the Benzene standard states, "The methods that can be used to reduce employee exposure to benzene include conventional technologies such as air monitoring, double mechanical seals, exhaust ventilation, leak detection and repair […]. These controls can be used in combination. So, if one engineering control is not sufficient, additional ones can be utilized." 52 FR 34460, 34511 (Sept. 11, 1987). Likewise, in the preamble to the Butadiene standard, OSHA noted that one of the controls applicable to the production of butadiene monomer and polymers is pumps equipped with dual seals. 61 FR 56746, 56810 (Nov. 4, 1996).

Leak detection is an important part of complying with these standards. OSHA noted leak detection and repair as an available control in the Benzene standard, 52 Fed. Reg. at 34461, and requires the development and implementation of periodic leak detection surveys in any compliance plan required under the Butadiene standard, 29 CFR §1910.1051(f)(2)(ii).

Question 2: Are conventional non-bellow, non-leak proof, non-double seal valves considered to be forms of engineering control?

Response: Yes, conventional non-bellow, non-leak proof, non-double seal valves would be considered engineering controls, as OSHA noted in the Benzene standard: "Types of controls available include leak detection and repair, vapor recovery, automated sampling, dual seal valves, enclosures and many others." 52 FR 34460, 34461 (1987). The Benzene standard and the Butadiene standard are generally performance-oriented standards, and employers may develop a combination of engineering and work practice controls suited for their specific facilities. Therefore, if the non-bellow, non-leak proof, non-double seal valves are more suited to an employer's specific facility process, such as where minimal pressure is involved and the potential for leakage may not be a significant concern, then they would be acceptable as long as employee exposures remain at or below permissible limits.

Question 3: If conventional type valves are to be specified in Butadiene and Benzene services, are there recommended fugitive emissions threshold limits in which the valve needs to be changed or replaced?

Response: Seals may be an effective control method. The U.S. Environmental Protection Agency (EPA) had reported that double mechanical seals in pumps and compressors have an efficiency of nearly 100 percent in controlling benzene emissions. 52 FR 34460, 34513. Please note that leak detection surveys help employers comply with these standards and, as noted above, the Butadiene standard requires the development and implementation of periodic leak detection surveys in employers' compliance programs, and requires a leak prevention, detection and repair program in any required exposure goal program. 29 CFR §1910.1051(f)(2)(ii), 1051(g)(5)(i). For fugitive emissions threshold limits of mechanical seals and valves, OSHA expects employers to follow manufacturers' instructions for process equipment, any applicable environmental regulations for fugitive emissions, and recommends following applicable industry standards.

Thank you for your interest in occupational safety and health. I hope you find this information helpful. OSHA's requirements are set by statute, standards, and regulations. Letters of interpretation do not create new or additional requirements but rather explain these requirements and how they apply to particular circumstances. This letter constitutes OSHA's interpretation of the requirements discussed. From time to time, letters are affected when the agency updates a standard, a legal decision impacts a standard, or changes in technology affect the interpretation. To assure that you are using the correct information and guidance, please consult OSHA's website at www.osha.gov. If you have further questions, please feel free to contact the Office of Health Enforcement at (202) 693-2190.

Sincerely,

Erin P. Gilmore, Acting Director
Directorate of Enforcement Programs