May 31, 2023

Mr. Troy Robins
Suburban Manufacturing Group
10531 Dalton Avenue NE
Monticello, Minnesota 55362

Dear Mr. Robins:

Thank you for your letter to the Occupational Safety and Health Administration (OSHA), Directorate of Enforcement Programs. Your letter requested clarification of OSHA's Respiratory Protection standard, 29 CFR § 1910.134, specifically pertaining to paragraph 29 CFR § 1910.134(i), Breathing air quality and use. This letter constitutes OSHA's interpretation only of the requirements discussed herein and may not be applicable to any questions not delineated within your original correspondence.

Background: The Suburban Manufacturing Group manufactures filtration and drying systems for compressed air. A part of the product line is a compressed air filtration system for use with supplied air respirators (SARs). You have asked for OSHA's interpretation on addressing air quality, as well as clarification on various designs or configurations of currently marketed breathing air systems.

Please be aware that OSHA does not approve or endorse any specific equipment, products, or manufacturers' designs, therefore any questions about specific equipment or diagrams will only be answered in general terms. Below are your paraphrased questions and our responses, including feedback, when possible, on your proposed system.

Question 1: Have the specifications for Grade D air changed since its 1989 incorporation into OSHA's Respiratory Protection standard, 29 CFR § 1910.134?

Response: No, OSHA's specifications for Grade D air have not changed. 29 CFR § 1910.134(i)(1)(ii) specifies that Grade D air must meet the American National Standards Institute (ANSI)/Compressed Gas Association (CGA) Commodity Specification for Air, G-7.1-1989. Your letter refers to an updated consensus CGA standard, G-7.1-2018. Per OSHA's Field Operations Manual, CPL-02-00-164, if an employer chooses to comply with an amended consensus standard rather than the one referenced in a regulation – and that consensus standard provides equal to or greater protection than the standard referenced in the regulation (e.g., 29 CFR § 1910.134) – the employer's deviation from the cited standard will be considered a de minimis condition. De minimis conditions are those where an employer has implemented a measure different from one specified in a standard that has no direct or immediate relationship to safety or health. See https://www.osha.gov/enforcement/directives/cpl-02-00-164/.

Question 2: What is the acceptable dryness of air?

Response: The acceptable dryness of air will vary depending on whether the breathing air supplied to respirators comes from an air cylinder versus an air compressor. When using a cylinder, employers must ensure that the moisture content in the self-contained breathing apparatus (SCBA) cylinder does not exceed a dew point of -50°F (-45.6°C) at one atmosphere pressure. See 29 CFR § 1910.134(i)(4)(iii). However, if employers are instead using compressors to supply breathing air to respirators, the moisture content must be minimized so that the dew point at one atmosphere is 10°F (5.56°C) below the ambient temperature. See 29 CFR § 1910.134(i)(5)(ii). ANSI/CGA G-7.1-1989, Table 2, Moisture Conversion Data, provides information on the acceptable dryness of air (converted from the dew point).

Question 3: A supplied air respirator (SAR) is being used in an ambient temperature of 70°F and is receiving air from a compressed air system maintaining a system pressure of 120 psig. A drying system, as a part of the industrial compressed air system, is utilized to provide a dew point in the compressed air at or below 40°F. Would this dew point meet OSHA regulations?

Response: Without more information, we cannot determine if this dew point would meet OSHA regulations. OSHA generally refrains from solving calculations for specific equipment when an OSHA representative did not collect, or was not present, when the readings were taken, because OSHA cannot ascertain that the data is complete or accurate.

In general, the moisture content of compressed air must be kept to a minimum to prevent water from freezing in valves and connections of the air supply system. Such freezing can block air lines, fittings, and pressure regulators. See 63 FR1254, January 8, 1998. To ensure low moisture content of ambient air, 29 CFR § 1910.134(i)(5)(ii) requires that the dew point at one atmosphere pressure of breathing air supplied by a compressor must be 10°F (5.56°C) below the ambient temperature (e.g., in plant). See OSHA's Small Entity Compliance Guide for the Respiratory Protection Standard, available at https://www.osha.gov/Publications/3384small-entity-for-respiratory-protection-standard-rev.pdf, page 51. See also response to question 1.

Question 4: Does 29 CFR § 1910.134(i)(4)(iii) apply to compressed air systems used for supplied air respirators?

Response: No, 29 CFR § 1910.134(i)(4)(iii) only applies to the moisture content in the SCBA cylinders used to supply breathing air to respirators. By contrast, 29 CFR § 1910.134(i)(5) applies to compressors.

Question 5: Does OSHA deem the requirements of 29 CFR § 1910.134(i)(4)(iii) to be too dry for SARs?

Response: 29 CFR § 1910.134(i)(4)(iii) governs the moisture content in SCBA cylinders while 29 CFR § 1910.134(i)(5)(ii) governs the moisture content in an air compressor for airline respirators. The two systems — an air compressor that supplies air to a SAR and the supply of air in SCBA cylinders — are different, and OSHA's applicable requirements for each system must not be interchanged.

Question 6: Can "exceed" be defined, as used in 29 CFR § 1910.134(i)(4)(iii)? Does it mean that the moisture content has to be at -50°F or lower? Does it mean that the dew point cannot be below -50°F?

Response: 29 CFR § 1910.134(i)(4)(iii) states the moisture content in SCBA cylinders of breathing air cannot exceed a dew point of -50°F (e.g., -49°F, -48°F, or higher temperatures). This means the dew point temperature must be at -50°F or lower at one atmosphere, such as at -51°F, etc.

Question 7: To achieve a -50°F dew point at 1 atmosphere, an air system operating at 120 psig should then have a dew point of -13.4 °F at 120 psig; would this then be the minimum dew point to meet specification?

Response: As mentioned in response 3, OSHA does not generally solve calculations for specific equipment. The answer to this question would depend on whether the air system is a breathing air compressor or for an SCBA air cylinder. Please refer to the response to question 5 above.

Question 8: Can "suitable" be defined, as used in 29 CFR § 1910.134(i)(5)(iii), that compressors used to supply breathing air to respirators must have "suitable in-line air-purifying sorbent beds and filters to further ensure breathing air quality. Sorbent beds and filters shall be maintained and replaced or refurbished periodically following the manufacturer's instructions?"

Response: The term "suitable" means that the compressor is capable of delivering a continuous supply of Grade D breathing air. To ensure breathing air quality, the air-purifying sorbent beds and the filters must be changed and maintained in accordance with manufacturers' instructions. Please refer to OSHA's August 3, 1998 memorandum, Questions and Answers on the Respiratory Protection Standard, for this definition and more information on suitable in-line air-purifying sorbent beds and filters.

Question 9: Would OSHA consider incorporating the specifications identified by the International Organization of Standardization (ISO) 8573-1? This ISO 8573-1 establishes clear limits regarding particle size and quantity, dew point, and oil content, and could provide a little more clarity.

Response: 29 CFR § 1910.134 cannot incorporate specifications identified by ISO without proper rulemaking procedures to change the current version of the standard.

Question 10: Is there a standard for allowable materials and piping configurations? For instance: can compressors use a flow control device (such as a regulator) that restricts the flow in one direction? Is there a maximum distance allowed between the wall-mounted breathing air filtration and the operator's mask? What type of pipe or hose can be used with the breathing air filtration unit and individual respirable air connections (plumb rigid, etc.)?

Response: 29 CFR § 1910.134 does not include any information or requirements specifying materials and piping configurations. As stated above, OSHA does not endorse or approve products, nor is it able to comment on the appropriateness of the various system configurations available in the market. Also, OSHA is not a testing or approval agency, and thus, does not specify the location of filters or other mechanical components of the air compressor and respirator. This is the responsibility of the National Institute for Occupational Safety and Health (NIOSH). Respirators are certified by NIOSH as a complete assembly. OSHA depends heavily upon the expertise at NIOSH to evaluate respirators and their components. NIOSH's National Personal Protective Technology Laboratory (NPPTL) provides a testing, approval, and certification program assuring respirators used in the workplace meet the standards at 42 CFR Part 84. Please note that 29 CFR § 1910.134(d)(1)(ii) requires the employer to select a NIOSH-certified respirator and all parts of the respirator, including the assembly, must be configured and used in the same manner as specified in the NIOSH certification of the respirator.

If you have questions concerning respirator certification, please contact NIOSH's NPPTL Conformity Verification and Standards Development Branch at cvsdbadmin@cdc.gov or 412-386-4000. NPPTL can be contacted at 626 Cochrans Mill Road, Pittsburgh, PA 15236, 1-800-CDC-INFO (1-800-232-4636), outside the U.S. 412-386-6111, 1-888-232-6348 TTY.

Finally, note that ANSI/CGA G-7.1-1989, ANSI Z88.2, and the manufacturer, are good resources for the proper use, maintenance, and general information on respirator assembly and their components.

Question 11: At what point is the air going to a NIOSH-approved hose and respirator assembly deemed breathing air quality in order to satisfy OSHA standards?

Response: Section 29 CFR § 1910.134(i) specifies OSHA's requirements for breathing air quality. For questions concerning respirator certification (i.e., air flow through the respirator assembly), please contact NIOSH's Conformity Verification and Standards Development Branch mentioned in the response to question 10 above. Compressed air sources must have the capacity to provide adequate air quality, quantity, and flow of breathing air. The NIOSH letter referenced in your letter to us, Letter to All Users of Supplied-Air Respirators Use of Unapproved Supplied-Air Respirators in the Paint Spray and Automotive Refinishing Industries, dated May 23, 1996, states, "The current regulations (42 CFR Part 84.141) require that Grade D or higher quality air be supplied to the supplied-air respirator at the point where the NIOSH approved air-supply hose connects to the respirable air source." Please note that this letter has been archived and is no longer being updated by NIOSH. OSHA recommends that you contact NIOSH's NPPTL to confirm the accuracy of the information in their archived letter.

Other good resources to use are ANSI/CGA G-7.1-1989, which has test procedures given in sections 4 and 5 of their consensus standard, and ANSI Z88.2-1992, Section 10.5.4.3, which recommends, "–[a]s part of acceptance testing, and prior to initial use, representative sampling of the compressor air output shall be performed to ensure that it complies with the requirements in sections 10.5.1 and 10.5.4. To ensure a continued high quality air supply, and to account for any distribution system contaminant input, a representative sample should be taken at distribution points."

Question 12: If the NIOSH-approved, belt-mounted, in-line filters provide the final filtration to meet the Grade D breathing air specification, without which the air would not meet the criteria, are these systems then meeting OSHA standard and NIOSH policy?

Response: OSHA is not a respirator testing and approval agency; this responsibility belongs to NIOSH NPPTL. Please contact NIOSH's NPPTL for assistance with understanding the requirements of 42 CFR Part 84.

Question 13: According to NIOSH's Respirator User Notices, only the system's NIOSH-approved hose is technically useable for breathable air as long as the hose and filter are NIOSH-approved and the required NIOSH-approved, belt-mounted, in-line carbon filter is used to remove the odors in the air system. Is this system design allowed under OSHA regulations or standards? Is there a specific OSHA regulation or standard that states an employer must have a NIOSH-approved hose to run from a wall-mounted filter to a belt filter?

Response: Please see response to question 12. OSHA also does not interpret NIOSH Respirator User Notices. 29 CFR § 1910.134(d)(1)(ii) requires the employer to select a NIOSH-certified respirator. As stated in the response to question 10 above, all parts of the respirator, including the assembly, must be configured and used in the same manner as specified in the NIOSH certification of the respirator.

Question 14: What is OSHA's interpretation of a system with a standard (or NIOSH-approved) breathing (Grade D air quality) air hose connected to a belt-mounted flow control device that contains a work line, where the work line disconnect couplers are different from the couplers for the breathing air disconnect? Stated differently, if the connection points for the respirable air and pneumatic tool (work line) are separated with different couplers, would this design be considered appropriate and acceptable by OSHA? Does it allow for the potential health and safety hazard stated by NIOSH?

Response: If the respirator and the entire assembly are not NIOSH-approved, then they are not in compliance with OSHA regulations under 29 CFR § 1910.134. Please also see our letters of interpretation on belt-mounted filtration units used with any NIOSH-approved supplied-air respirator to Mr. Charles E. Martin, dated September 4, 1996, and on couplings used in supplied-air respirator systems to Mr. G.T. Slay, dated April 24, 1986, that specify that NIOSH does not evaluate or approve belt mounted filtration systems that incorporate a discharge port to supply process air and breathing air couplings must be incompatible with outlets for nonrespirable worksite air or other gas systems, respectively.

Question 15: Would OSHA consider incorporating the concerns identified by NIOSH, related to system contaminants in respirable air, in its regulations?

Response: OSHA and NIOSH worked together when OSHA developed the Respiratory Protection standard. OSHA standards must go through rulemaking procedures to make changes to the current version of the standard. This issue is not on the current regulatory agenda.

Question 16: What are OSHA's requirements for the use of matched or paired hoses, masks, or hoods? Should all pieces be manufactured by the same company?

Response: Respirator parts from different manufacturers or respirator models cannot be interchanged, as this would void the NIOSH certification. See June 20, 1997, Memorandum SCBA Cylinder Interchangeability, https://www.osha.gov/laws-regs/standardinterpretations/1997-06-20-0.

As you may be aware, Minnesota is one of 29 states or territories that operate its own occupational safety and health program under a plan approved and monitored by federal OSHA. Employers in Minnesota must comply with state occupational safety and health requirements. As a condition of plan approval, State Plans are required to adopt and enforce occupational safety and health standards that are at least as effective as those promulgated by federal OSHA. A state's interpretation of their standards must also be at least as effective as federal OSHA interpretations. If you would like further information regarding Minnesota's occupational safety and health requirements, you may contact them at:

Minnesota Department of Labor and Industry
443 Lafayette Road North
St. Paul, Minnesota 55155-4307
Telephone: (651) 284-5050
https://www.osha.gov/dcsp/osp/stateprogs/minnesota.html

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 https://www.osha.gov. If you have further questions, please feel free to contact the Office of Health Enforcement at (202) 693-2190.

Sincerely,

Kimberly A. Stille, Director
Directorate of Enforcement Programs