Subpart H
A gaseous hydrogen system is a supply system in which hydrogen is delivered, stored, and discharged in the gaseous form to the consumer's piping and includes the containers, regulators, relief devices, manifolds, interconnecting piping and controls up to the point where hydrogen first enters the consumer's distribution piping. See 1910.103(a)(1)(i).
“Approved” and “Listed” mean that equipment has been accepted or certified by a nationally recognized testing laboratory unless the standard indicates otherwise. See 1910.103(a)(1)(ii) and 1910.103(a)(1)(iii); also refer to the definition of a nationally recognized testing laboratory at 1910.7.
“ASME” refers to the American Society of Mechanical Engineers, which is the consensus body whose codes (when referenced) set construction and testing requirements for pressure vessels and related equipment. See 1910.103(a)(1)(iv).
“DOT Specifications” are the U.S. Department of Transportation regulations in 49 CFR Chapter I that govern the design, construction, and testing of containers; hydrogen containers may be required to meet DOT Specifications where that option is allowed. See 1910.103(a)(1)(v) and 1910.103(a)(1)(vi).
Paragraph (b) does not apply when the gaseous hydrogen system has a total hydrogen content of less than 400 cubic feet or when the site is a hydrogen manufacturing plant or a supplier-operated refilling operation for portable containers, trailers, mobile supply trucks, or tank cars. See 1910.103(a)(2)(i)(a) and 1910.103(a)(2)(i)(b).
Paragraph (c) does not apply to liquefied hydrogen portable containers with a capacity of less than 150 liters (39.63 gallons), nor to liquefied hydrogen manufacturing plants or supplier operations that store and refill portable containers, trailers, mobile supply trucks, or tank cars. See 1910.103(a)(2)(ii)(b).
Hydrogen containers must either be designed, constructed, and tested per the ASME Boiler and Pressure Vessel Code, section VIII - Unfired Pressure Vessels (1968), or be designed, constructed, tested and maintained in accordance with DOT Specifications and Regulations under which they are fabricated. See 1910.103(b)(1)(i)(a)(1) and 1910.103(b)(1)(i)(a)(2).
Permanently installed hydrogen containers must be provided with substantial noncombustible supports on firm noncombustible foundations to prevent settling or movement that could damage the container or piping. See 1910.103(b)(1)(i)(b).
Each portable container must be legibly marked with the name "Hydrogen" in accordance with the marking requirements referenced in [1910.253(b)(1)(ii)]. See 1910.103(b)(1)(i)(c) and the related 1910.253(b)(1) material for marking details.
Hydrogen containers must be equipped with safety relief devices required by the ASME Boiler and Pressure Vessel Code, section VIII, or by the DOT Specifications under which the container was fabricated; the devices must discharge upward and unobstructed to open air to avoid impingement, except for DOT containers with internal volume of 2 cubic feet or less; and relief devices or vent piping must be protected against moisture collection and freezing that would prevent proper operation. See 1910.103(b)(1)(ii)(a), 1910.103(b)(1)(ii)(b), and 1910.103(b)(1)(ii)(c).
Piping, tubing, and fittings must be suitable for hydrogen service at the pressures and temperatures involved, and cast iron pipe and fittings shall not be used for hydrogen. See 1910.103(b)(1)(iii).
Hydrogen piping and tubing shall conform to the ANSI B31.1 Industrial Gas and Air Piping Code (with addenda) as incorporated by reference, and joints may be made by welding, brazing, or flanged, threaded, socket, or compression fittings; gaskets and thread sealants must be suitable for hydrogen service. See 1910.103(b)(1)(iii)(b) and 1910.103(b)(1)(iii)(c).
Valves, gauges, regulators, and other accessories must be suitable for hydrogen service; installations must be supervised by personnel familiar with hydrogen system practices; equipment must be readily accessible and protected from damage and tampering; control cabinets must be adequately ventilated; mobile supply units must be secured against movement and electrically bonded before discharge. See 1910.103(b)(1)(iv)(a)-(f).
Hydrogen storage locations must be permanently placarded with “HYDROGEN - FLAMMABLE GAS - NO SMOKING - NO OPEN FLAMES” or an equivalent warning. See 1910.103(b)(1)(v).
After installation, all piping, tubing, and fittings must be tested and proved hydrogen gas tight at maximum operating pressure. See 1910.103(b)(1)(vi).
Hydrogen systems must be readily accessible to delivery equipment and authorized personnel, located above ground, not placed beneath electric power lines, not located close to flammable liquid piping or other flammable gas piping, and, when near aboveground flammable liquid storage, be on higher ground unless dikes/diversion curbs or solid walls prevent liquid accumulation under the system. See 1910.103(b)(2)(i)(a)-(e).
Table H‑1 ranks preferred locations by system size: systems less than 3,000 cubic feet should be located outdoors (I); systems 3,000 to 15,000 cubic feet preferably in separate buildings (II); systems over 15,000 cubic feet preferably outdoors or in specifically permitted locations—consult the table for the exact classification. See 1910.103(b)(2)(ii)(a).
Minimum separation distances vary by system capacity and type of exposure; for example, a system under 3,000 CF must be 10 feet from a wood-frame building, while a system over 15,000 CF must be 50 feet. Table H‑2 lists detailed minimum feet distances for buildings, wall openings, flammable liquid storage, ventilation inlets, concentrations of people, and more. See 1910.103(b)(2)(ii)(b) and the full Table H‑2 in 1910.103(b)(2)(ii).
Hydrogen systems under 3,000 CF located inside buildings and exposed to other occupancies must be in an adequately ventilated area, at least 20 feet from stored flammable materials or oxidizing gases, 25 feet from open flames and other ignition sources, 25 feet from concentrations of people, 50 feet from ventilation intakes and other flammable gas storage, protected against falling object damage, and multiple small systems must be separated by at least 50 feet if more than one is installed in the same room. See 1910.103(b)(2)(ii)(d)(1)-(8).
Special rooms must provide adequate ventilation to the outdoors with inlet openings near the floor and outlet openings at the high point; inlet and outlet openings must each have at least 1 square foot per 1,000 cubic feet of room volume. Explosion venting must be provided to exterior walls or roof with vent area equal to at least 1 square foot per 30 cubic feet of room volume, and venting may be walls of light noncombustible material, lightly fastened hatch covers, outward-opening doors, or designs that relieve at a maximum pressure of 25 psf. See 1910.103(b)(3)(ii)(b) and 1910.103(b)(3)(ii)(c).
Electrical equipment in special rooms must comply with Subpart S of 29 CFR 1910 for Class I, Division 2 hazardous locations, which addresses electrical equipment and wiring methods suitable for atmospheres where flammable gases may occasionally be present. See 1910.103(b)(3)(ii)(e) and the broader 1910 provisions for Subpart S.
Special rooms housing hydrogen systems must have floors, walls, and ceilings with a fire-resistance rating of at least 2 hours. See 1910.103(b)(3)(iii)(a).
Each mobile hydrogen supply unit used as part of a hydrogen system must be electrically bonded to the stationary system before discharging hydrogen to prevent static or stray currents that could create ignition sources. See 1910.103(b)(1)(iv)(f).
The requirement that safety relief devices discharge upward and unobstructed to open air does not apply to DOT Specification containers that have an internal volume of 2 cubic feet (about 56.6 liters) or less; all other containers must discharge upward and unobstructed. See 1910.103(b)(1)(ii)(b).
If stored hydrogen on site in one location reaches or exceeds the PSM threshold quantity (10,000 pounds) and hydrogen meets the Category 1 flammable gas definition, the storage and on-site activities (use, storage, handling, movement) qualify as a PSM-covered process and subject the site to 29 CFR 1910.119. OSHA's interpretation about aggregating flammable gases toward the PSM threshold explains that pre‑charged equipment stored on-site can be included when the aggregate quantity exceeds the threshold. See 1910.119 and OSHA's interpretation on flammable gas aggregation at https://www.osha.gov/laws-regs/standardinterpretations/2024-06-06.
Relief devices and vent piping must be arranged or located so that moisture cannot collect and freeze and interfere with the proper operation of the device; locate vents to avoid water traps and consider insulation or heat tracing where freezing is possible. See 1910.103(b)(1)(ii)(c).
Storage containers, piping, valves, regulators and accessories must be readily accessible and protected against physical damage and tampering; cabinets or housings containing hydrogen control or operating equipment must be adequately ventilated to prevent gas buildup. See 1910.103(b)(1)(iv)(c)-(d).
Hydrogen systems under 3,000 CF inside buildings and exposed to other occupancies must be at least 50 feet from ventilation or air-conditioning intakes and at least 50 feet from other flammable gas storage. See 1910.103(b)(2)(ii)(d)(5)-(6).
Electrical equipment within 15 feet of an outdoor hydrogen location must comply with the electrical provisions of Subpart S of 29 CFR 1910 to ensure equipment and wiring are suitable for the hazard presented. See 1910.103(b)(3)(i)(c) and consult 1910 Subpart S requirements.
Each manifolded hydrogen supply unit must be legibly marked with the name "Hydrogen" or with a legend such as "This unit contains hydrogen" so that the contents are clear to personnel. See 1910.103(b)(1)(ii) marking text and related provisions.
You must build storage/handling rooms with walls or partitions that are continuous floor-to-ceiling, securely anchored, and include at least one exterior wall. See 1910.103(b).
Ventilation must be provided as required in 1910.103(b)(3)(ii)(b), and rooms must follow the specific ventilation design called out by 1910.103(b)(3)(iii)(b).
Yes — explosion venting must be provided as specified in 1910.103(b)(3)(ii)(c), and 1910.103(b)(3)(iii)(c) points you to that requirement.
No — there shall be no sources of ignition from open flames, electrical equipment, or heating equipment in those hydrogen areas per 1910.103(b)(3)(iii)(d).
Electrical equipment must meet the requirements of subpart S for Class I, Division 2 locations as required by 1910.103(b)(3)(iii)(e).
Heating, if provided in hydrogen storage areas, must be by steam, hot water, or indirect means as required by 1910.103(b)(3)(iii)(f).
You must keep legible operating instructions at the operating locations for any installation that requires user operation, per 1910.103(b)(4).
All charged gaseous hydrogen equipment must be maintained in a safe operating condition in accordance with the section's requirements, as stated in 1910.103(b)(5).
The area within 15 feet of any hydrogen container must be kept free of dry vegetation and combustible material as required by 1910.103(c).
Stationary storage containers must meet ASME Boiler and Pressure Vessel Code, Section VIII (1968) or applicable API Standard 620 provisions, and portable containers must meet DOT specifications, per 1910.103(c)(1)(i)(a) and 1910.103(c)(1)(i)(b).
Permanently installed containers must be on substantial noncombustible supports securely anchored to firm noncombustible foundations, and steel supports over 18 inches high must have a protective coating with a 2-hour fire-resistance rating as required by 1910.103(c)(1)(ii).
Each liquefied hydrogen container must be legibly marked “LIQUEFIED HYDROGEN - FLAMMABLE GAS” as required by 1910.103(c)(1)(iii).
Safety relief devices must be sized per CGA Pamphlet S-1 for stationary containers or DOT requirements for portable containers, must discharge unobstructed to the outdoors to avoid impingement, and must be arranged to prevent moisture freeze interference, as required by 1910.103(c)(1)(iv)(a)(1), 1910.103(c)(1)(iv)(a)(2), 1910.103(c)(1)(iv)(b), and 1910.103(c)(1)(iv)(c).
Safety relief devices must be provided in piping wherever liquefied hydrogen could be trapped between closures, per 1910.103(c)(1)(iv)(d).
Piping, tubing, fittings, and sealants must be suitable for hydrogen service at the pressures and temperatures involved; joints should preferably be welded or brazed (flanged, threaded, or compression fittings allowed), and means must be provided to minimize personnel exposure to low-temperature piping, as required by 1910.103(c)(1)(v) and 1910.103(c)(1)(v)(c).
Only insulating materials rated nonburning per ASTM D1692-68 may be used; insulation must have a vapor-tight outer seal to prevent air condensation and oxygen enrichment, and insulation and shields must prevent attrition, per 1910.103(c)(1)(v)(e).
Valves, gauges, regulators, and other accessories must be suitable for liquefied hydrogen service; a shutoff valve must be located as close to the container as practical, and containers over 2,000 gallons must have a remote control shutoff with no intervening connections, while cabinets or housings with hydrogen control equipment must be ventilated, per 1910.103(c)(1)(vi)(a)-(d).
After installation, all field-erected piping must be tested and proved hydrogen gas-tight at operating pressure and temperature; containers out of service for over one year must be inspected and tested similarly and safety relief devices checked for operation and set correctly, per 1910.103(c)(1)(vii)(a)-(b).
Vaporizers must be anchored, have sufficiently flexible connecting piping to accommodate thermal expansion/contraction, be protected with safety relief devices on hydrogen and heating-media sections, use indirect heat (air, steam, water), and include a low-temperature shutoff in the discharge piping to prevent flow if the heat source is lost, as required by 1910.103(c)(1)(viii)(a)-(d).
Electrical wiring and equipment within 3 feet of regularly made/broken connections must meet subpart S for Class I, Group B, Division 1; except as noted, wiring and equipment within 25 feet of such connection points or within 25 feet of a liquid hydrogen storage container must meet Class I, Group B, Division 2 requirements per 1910.103(c)(1)(ix)(a)-(b).