Applicability. PERSONNEL AND EQUIPMENT PROTECTION

In oil and gas producing operations and gas processing plant operations, severity of the environment shall be as­sessed. As a minimum, the following measures shall be im­plemented:

a. Personnel protection should be provided if the work area
concentration of hydrogen sulfide (refer to Par. 3.8) exceeds
10 ppm eight-hour time weighted average (TWA) or 15 ppm
as a short term exposure level (STEL) averaged over 15 min­
utes (refer to Appendix A); or the work area concentration of
sulfur dioxide (refer to Par. 3.16) exceeds 2 ppm as an eight-
hour TWA or 5 ppm as a STEL averaged over 15 minutes
(refer to Appendix B). Personnel safety provisions of this
publication do not apply when:

1. the atmospheric concentration of hydrogen sulfide could
not exceed 10 ppm (by volume), or

2. the atmospheric concentration of sulfur dioxide could not
exceed 2 ppm (by volume).

b. Equipment and materials shall be selected on the basis of
resistance to sulfide stress cracking and corrosion. Refer to
Section 8, "Design and Construction Practices" Appendix D,
and NACE Standard MR0175 for recommendations for se­
lection of equipment and materials. The equipment and ma­
terials provisions of this publication do not apply when the
partial pressure of hydrogen sulfide in the gas could not ex­
ceed 0.05 psia or 10 psia in the gas phase of sour crude sys­
tems (refer to Appendix D, Par. D.I.I.2).

Some conditions may require extensive personnel safety measures but only the use of conventional equipment and materials; other conditions may require the use of special equipment and materials but only minimal personnel safety

measures; still other conditions may require both.

Throughout this publication, "trigger levels" for various actions are used to ensure safety of employees and the pub­lic. These trigger levels have been established considering threshold limit values (TLVs—refer to Par. 3.17). These TLVs are subject to change and users should check the latest edition of Threshold Limit Values and Biological Exposure Indices and the latest revision of 29 Code of Federal Regu­lations Part 1910.1000, "Toxic and Hazardous Substances", for compliance.

In 1989, the U. S. Department of Labor, Occupational Safety and Health Administration (OSHA) issued updated permissible exposure limits (PELs) for several hundred chemicals, including revised PELs for hydrogen sulfide (10 ppm as an eight-hour TWA or 15 ppm STEL averaged over 15 minutes) and sulfur dioxide [2 ppm as an eight-hour TWA or 5 ppm STEL averaged over 15 minutes (refer to 54 Fed­eral Register (FR) 2333, January 19,1989]. A federal court set aside the OSHA 1989 rule (refer to 58 Federal Register 35338, June 30,1993).

The American Conference of Governmental Industrial Hygienists (ACGIH) recommends a hydrogen sulfide TLV of 10 ppm (eight-hour TWA) and a STEL of 15 ppm aver­aged over 15 minutes and recommends 2 ppm as an eight-hour TWA TLV and 5 ppm as a STEL averaged over 15 minutes for sulfur dioxide (refer to Threshold Limit Values for Chemical Substances and Biological Exposure Indices).

In the interest of safety and health, this standard recom­mends use of the ACGIH TLVs (refer to Threshold Limit Values for Chemical Substances and Biological Exposure In­dices 1993-94) as trigger levels for employee safety (refer to Appendices A and B). Some states have adopted these levels as requirements for personal safety.

Individual employers may set their own trigger levels af­ter review and due consideration of site specific conditions, various regulatory requirements, and material safety data sheet (MSDS) information. Users should check the current status of OSHA PELs, OSHA acceptable ceiling concentra­tions (ACCs), ACGIH TLVs, and applicable regulatory re­quirements concerning substances of interest.