LP gas storage definitions

Adequate ventilation means the gas concentration in air is kept below 25% of the lower flammable limit during normal operation. In other words, ventilation is sufficient when the gas‑air mixture concentration does not exceed one‑quarter of the LFL, which prevents a flammable atmosphere under normal conditions. See 1910.110(a)(13) for the definition and general 1910.110 for context.

LP‑Gas must be effectively odorized so a distinct odor is detectable at concentrations no greater than one‑fifth of the lower flammable limit, unless odorization would be harmful to the intended use or further processing or would serve no useful warning purpose. That means you generally must add an approved odorant to LP‑Gas so people can detect small leaks, but you may omit odorization if it interferes with safe processing or product use. See 1910.110(b)(1)(i) and the overall 1910.110(b) rules.

Using 1.0 lb of ethyl mercaptan, 1.0 lb of thiophane, or 1.4 lb of amyl mercaptan per 10,000 gallons of LP‑Gas is an acceptable method to meet the odorization requirement. These listed quantities are provided as a means of compliance, but the rule does not prohibit use of other odorants that achieve the detection level required by [1910.110(b)(1)(i)]. See 1910.110(b)(1)(ii) and 1910.110(b).

A “container” is any vessel such as a tank, cylinder, or drum used to transport or store LP‑Gas, and a “container assembly” is the container together with its fittings for openings (valves, excess‑flow valves, liquid‑level gaging, relief devices, and protective housings). In practice, treat the physical tank or cylinder as the container and the complete set of attached valves and devices as the container assembly that must meet applicable requirements. See 1910.110(a)(4) and 1910.110(a)(3).

Containers used with most systems must be designed, constructed, and tested to the ASME Boiler and Pressure Vessel Code, section VIII, Division 1 (1968 edition), or, for older API‑ASME tanks fabricated before July 1, 1961, the API‑ASME Code identified in paragraph (b)(3)(iii). That means new aboveground LP‑Gas tanks should be ASME‑constructed and stamped accordingly, while certain older API‑ASME tanks may be acceptable if they meet the dates and addenda described in the rule. See 1910.110(b)(3)(i) and 1910.110(b)(3)(iii).

Each applicable LP‑Gas container must have a metal nameplate stating compliance with the construction code or National Board stamping, whether it is for underground or aboveground use, the supplier name or trade name, and the water capacity in pounds or U.S. gallons. Ensure the nameplate is metal, attached where it stays visible after installation, and contains those specific data elements. See 1910.110(b)(5)(i)(a)–(d) and 1910.110(b)(5)(ii).

Nameplates must also list the design pressure in p.s.i.g., a warning about maximum allowed vapor pressure at 100 °F, tare weight for small containers (≤300 lb water capacity), maximum fill level markings for temperatures between 20 °F and 130 °F, and the outside surface area in square feet. These markings help users determine safe contents, handling, and fill limits. See 1910.110(b)(5)(i)(e)–(i).

Welding on pressure‑containing parts of a container must follow the code under which the tank was fabricated, and welding repairs to DOT containers must be done by a qualified manufacturer and comply with DOT regulations. That means you cannot perform structural welding to pressured shells unless you follow the original fabrication code, and DOT tanks requiring repair or modification must be returned to an authorized manufacturer for work compliant with 49 CFR requirements. See 1910.110(b)(4)(i) and 1910.110(b)(4)(ii).

System components such as container valves, connectors, manifold assemblies, and regulators must be approved or listed by a nationally recognized testing laboratory: DOT‑container systems must have approved valves and connectors; domestic/commercial systems (≤2,000 gal) require listed container assemblies and regulators; systems >2,000 gal require listing of individual regulators, valves, gages, and relief valves. In short, use listed/approved components appropriate to the container size. See 1910.110(b)(2)(i)–(iii).

When LP‑Gas and one or more other gases are stored or used in the same area, the containers must be marked to clearly identify their contents. This helps prevent accidental cross‑connection, mis‑use, or mixing of gases. See 1910.110(b)(5)(iii).

A DOT container is a vessel constructed according to applicable Department of Transportation regulations in 49 CFR chapter I, and a DOT cylinder is a cylinder that meets the requirements of 49 CFR chapter I. In practice, DOT‑spec containers and cylinders must meet transportation safety rules and are marked accordingly. See 1910.110(a)(6) and 1910.110(a)(19).

Containers and first stage regulators must be located outside buildings except in specific situations (charging rooms, portable use, LP‑Gas‑fueled engines/trucks, vehicles garaged per exceptions, or containers awaiting use/resale stored per paragraph (f)). Additionally, each container’s distance from important buildings must comply with Table H‑23 as required by [1910.110(b)(6)(ii)]. See 1910.110(b)(6)(i) and 1910.110(b)(6)(ii).

A vaporizer‑burner is an integrated unit that uses the heat from its burner to vaporize the liquid LP‑Gas (for example, for dehydrators or dryers), meaning the burner both supplies heat and vaporizes the fuel in one unit. Use this definition when evaluating equipment that relies on burner heat to convert liquid LP‑Gas to vapor for combustion. See 1910.110(a)(12).

P.S.I.G. means pounds per square inch gauge (pressure relative to ambient) and P.S.I.A. means pounds per square inch absolute (pressure relative to a perfect vacuum); both are important when specifying design and safe working pressures for containers and markings. Use P.S.I.G. for most container design pressure markings and P.S.I.A. when absolute pressure reference is required. See 1910.110(a)(9) and 1910.110(a)(10).

Yes—containers built to earlier ASME Code editions, subject to paragraph limits, and containers built and maintained under the NFPA No. 58 standard in effect at fabrication time may remain in use; specific exceptions apply for older ASME editions and API‑ASME containers fabricated prior to July 1, 1961. That means properly manufactured older tanks may be reinstalled or kept if they meet the listed allowances. See 1910.110(b)(3)(ii), 1910.110(b)(3)(iv), and 1910.110(b)(3)(iii).

An API‑ASME container refers to a tank constructed to the API‑ASME Code referenced in paragraph (b)(3)(iii), while an ASME container is built to the ASME Boiler and Pressure Vessel Code specified in paragraph (b)(3)(i); the distinction matters because the rule lists which code edition applies depending on the tank type and fabrication date. Check the applicable construction paragraph to confirm which code governs a specific tank. See 1910.110(a)(1) and 1910.110(a)(2) and the construction rules at 1910.110(b)(3).

Yes—OSHA will consider co‑located stored units that contain a Category‑1 flammable gas as part of the on‑site quantity for Process Safety Management threshold purposes; if the aggregate amount on site in one location equals or exceeds the 10,000‑pound threshold, the PSM standard applies. The OSHA interpretation on aggregating flammable gas quantities in co‑located pre‑charged appliances explains that storage and on‑site movement count toward the PSM process quantity. See the PSM aggregation interpretation at https://www.osha.gov/laws-regs/standardinterpretations/2024-06-06 and PSM applicability in 29 CFR 1910.119.

The minimum distance may be reduced to 10 feet for a single above‑ground container of 1,200 gallons water capacity or less if it is at least 25 feet from any other LP‑Gas container of more than 125 gallons water capacity. This exception appears in the table footnotes to Table H‑23; see 1910.110 Table H‑23 and footnote (2).

• If the single container meets the conditions above, the reduced 10‑foot distance can apply instead of the larger table distance.
• If you have multiple containers at a consumer site whose aggregate capacity is 501 gallons or greater, follow the aggregate‑capacity rules in Table H‑23 rather than the per‑container entries.

No. LP‑Gas containers installed for use shall not be stacked one above the other, as stated in 1910.110(b)(6)(iii).

• Stacking containers creates additional hazards and is expressly prohibited by the standard.

You must remove readily ignitible material such as weeds and long dry grass within 10 feet of any LP‑Gas container. This is required by 1910.110(b)(6)(vi).

• Keep this 10‑foot zone clear to reduce fire risk around containers.

The minimum separation between liquefied petroleum gas containers and flammable liquid tanks is 20 feet, and the minimum separation between a container and the centerline of a dike is 10 feet, as required by 1910.110(b)(6)(vii).

• Note the standard also includes exceptions when small containers are adjacent to small Class III tanks; see 1910.110(b)(6) and (b)(7).
• When dikes are used, no LP‑Gas containers may be located inside the diked area per 1910.110(b)(6)(ix).

The rule excepts the separation requirements when LP‑Gas containers of 125 gallons or less are installed adjacent to Class III flammable liquid tanks of 275 gallons or less capacity. This exception is noted in 1910.110(b)(6).

• Even with this exception you must still take suitable means to prevent accumulation of flammable liquids under LP‑Gas containers (diking, grading, diversion curbs) as required by 1910.110(b)(6)(viii).
• And LP‑Gas containers must not be placed inside diked areas used for flammable liquid tanks per 1910.110(b)(6)(ix).

Valves, fittings, and accessories connected directly to the container must have a rated working pressure of at least 250 p.s.i.g., be suitable for LP‑Gas service, and cast iron must not be used for container valves, fittings, and accessories (malleable or nodular iron is allowed for container valves). See 1910.110(b)(7)(i).

• This includes primary shutoff valves and other items attached directly to the container.
• Ensure material and design suitability for LP‑Gas service and the minimum 250 p.s.i.g. rating.

Connections to containers, except for safety relief connections, liquid level gaging devices, and plugged openings, shall have shutoff valves located as close to the container as practicable, as required by 1910.110(b)(7)(ii).

• The intent is to allow rapid isolation of the container by minimizing piping between the valve and the container.

Excess flow valves, where required, must close automatically at the rated vapor or liquid flows specified by the manufacturer; however, liquid level gaging devices that restrict outward flow to no more than a No. 54 drill size opening need not be equipped with excess flow valves. See 1910.110(b)(7)(iii) and 1910.110(b)(7)(iv).

• If an opening or gage is restricted to No. 54 drill size or smaller, the excess flow valve requirement for that opening does not apply.

Except as provided in 1910.110(c)(5)(i)(b), excess flow and back pressure check valves required by the section must be located inside the container or at a point outside where the line enters the container; installations outside must prevent undue strain that could cause breakage between the container and the valve, per 1910.110(b)(7)(vi).

• This placement protects the valve from external damage and avoids pipe breakage between the valve and container.

Yes. Excess flow valves shall be designed with a bypass not to exceed a No. 60 drill size to allow pressure equalization, as stated in the standard discussion (the text notes a No. 60 drill size opening to allow equalization) and related provisions in 1910.110(b)(7).

• The bypass is intended only to equalize pressure and must be limited to the specified drill size.

Containers of more than 30 gallons water capacity and less than 2,000 gallons water capacity that are filled on a volumetric basis and were manufactured after December 1, 1963, must be equipped for filling into the vapor space, per 1910.110(b)(7)(viii).

• This requirement reduces the risk of overfilling and liquid release during filling operations.

For vapor piping with operating pressures not exceeding 125 p.s.i.g., pipe must be suitable for at least 125 p.s.i.g. and be at least Schedule 40; for vapor piping over 125 p.s.i.g. and all liquid piping, pipe must be suitable for at least 250 p.s.i.g. and meet higher schedule requirements (Schedule 80 for threaded joints or at least Schedule 40 for welded joints), as specified in 1910.110(b)(8)(i)(a) and 1910.110(b)(8)(i)(b).

• Select pipe schedule and joint type according to operating pressure and whether joints are threaded or welded.

Tubing shall be seamless and of copper, brass, steel, or aluminum alloy, with copper tubing of Type K or L or equivalent as required by 1910.110(b)(8)(ii). When the gas in liquid form enters a building without pressure reduction, only heavy‑walled seamless brass or copper tubing with an internal diameter not greater than 3/32 inch and wall thickness not less than 3/64 inch may be used, as stated in 1910.110(b)(8)(iii).

• Use the specified heavy‑walled brass or copper for direct liquid entry to minimize leak and flow hazards inside buildings.

Aluminum alloy pipe is limited to a maximum nominal pipe size of three‑fourths inch and must not be used for pressures exceeding 20 p.s.i.g.; aluminum alloy pipe and tubing must be protected against external corrosion in certain conditions and shall not be installed within 6 inches of the ground, as required by 1910.110(b)(8)(i) and related paragraphs.

• Aluminum alloy pipe must be at least Schedule 40 and marked for compliance with ANSI/ASTM specs.
• Protect aluminum alloy pipe when contacting dissimilar metals or subject to repeated wetting; galvanized sheet steel may be used as protection.

Pipe joints may be screwed, flanged, welded, soldered, or brazed with filler material having a melting point exceeding 1,000 °F, and fittings must be designed for at least 125 p.s.i.g. for operating pressures ≤125 p.s.i.g. and at least 250 p.s.i.g. for pressures >125 p.s.i.g. The use of threaded cast iron pipe fittings (ells, tees, crosses, couplings, unions) is prohibited; aluminum alloy fittings must be used with aluminum alloy pipe or tubing, per 1910.110(b)(8)(iv), 1910.110(b)(8)(v), and 1910.110(b)(8)(vi).

• Ensure fittings selection matches operating pressure and material compatibility requirements.

Openings from a container or through fittings attached directly to a container to which a pressure gage connection is made need not be equipped with shutoff or excess flow valves if such openings are restricted to not larger than a No. 54 drill size opening, as provided in 1910.110(b)(7)(v) and 1910.110(b)(7)(iv).

• Restricting the opening size reduces potential release flow enough that extra valves are not required for those specific connections.

If the aggregate water capacity of multiple containers at a consumer site is 501 gallons or greater, the minimum distance requirements in Table H‑23 shall be applied using the aggregate capacity rather than per‑container capacity; see the Table H‑23 footnote (1) in 1910.110.

• If more than one installation is made, each installation must be separated from another installation by at least 25 feet.
• For such aggregate installations do not apply the "minimum distances between above‑ground containers" per the same footnote.

For 3/4 inch nominal copper tubing, the minimum wall thickness is 0.065 inch for Type K and 0.045 inch for Type L, as shown in Table H‑24 and discussed in 1910.110(b)(8)(ii).

• Use the table values to select tubing that meets the required wall thickness for safe LP‑Gas service.

When LP‑Gas in liquid form enters the building without pressure reduction, only heavy‑walled seamless brass or copper tubing with an internal diameter not greater than 3/32 inch and a wall thickness of not less than 3/64 inch shall be used, per 1910.110(b)(8)(iii).

• This requirement limits the size and increases robustness of tubing inside buildings where liquid gas is present.

Yes. In buildings devoted exclusively to gas manufacturing and distributing operations, the distances required by Table H‑23 may be reduced, but in no case may containers with water capacity exceeding 500 gallons be located closer than 10 feet to such buildings, according to 1910.110(b)(6)(v).

• Any reduction must still respect the 10‑foot minimum for containers >500 gallons.

OSHA considers storage of pre‑charged appliances that together contain a Category 1 flammable gas on site in one location to be a "process" under the PSM standard, and if the aggregate weight of the flammable gas in that location equals or exceeds the 10,000‑pound threshold the facility is subject to PSM, as explained in the PSM interpretation "PSM flammable gas aggregation" (June 6, 2024).

• The interpretation clarifies the PSM definition of "process" includes storage and on‑site movement, so aggregated charged refrigerant in pre‑charged units can trigger PSM coverage.
• Review 29 CFR 1910.119 and the cited interpretation to determine PSM applicability and compliance obligations.

Insulated fittings shall be used where aluminum alloy pipe or tubing connects with a dissimilar metal to prevent galvanic corrosion, as required by 1910.110(b)(8)(vi).

• Also protect aluminum alloy pipe against external corrosion where subject to repeated wetting or contact with dissimilar metals; galvanized sheet steel may be used for protection.

Yes. While excess flow and back pressure check valves are generally required to be inside the container or at the point where the line enters the container, an exception exists as provided in 1910.110(c)(5)(i)(b). See 1910.110(b)(7)(vi) for the general requirement.

• If you plan an installation that relies on the exception, review 1910.110(c)(5)(i)(b) for the specific conditions under which the valve may be located differently and ensure mechanical strains will not cause breakage between the valve and container.

No. When dikes are used with flammable liquid tanks, no liquefied petroleum gas containers shall be located within the diked area, as required by 1910.110(b)(6)(ix).

• Keep LP‑Gas containers outside diked areas to avoid pooling of flammable liquids under or around the LPG containers.

Hose must be made of materials that resist liquefied petroleum gas in both liquid and vapor forms. See the hose materials requirement in 1910.110(b)(9)(i).

• This means the hose compound (rubber, polymer, etc.) must be chemically compatible with LP‑gas so it will not degrade in service.
• If the hose uses wire braid reinforcement, that braid must be corrosion‑resistant (for example, stainless steel) per 1910.110(b)(9)(ii).

Hose subject to container pressure must be marked "LP‑Gas" or "LPG" at intervals no greater than 10 feet. See the marking requirement in 1910.110(b)(9)(ii).

• The marking helps identify pressurized LP‑gas hose segments so they can be inspected and handled correctly during installation, testing, and maintenance.

Hoses and hose connections must meet these minimum pressure requirements: bursting pressure for hoses subject to container pressure must be at least 1,250 p.s.i.g.; hose connections subject to container pressure must withstand a test pressure of at least 500 p.s.i.g. without leakage; and hose or connections on the low‑pressure side of the regulator must be designed for a bursting pressure of at least 125 p.s.i.g. See 1910.110(b)(9)(iii), 1910.110(b)(9)(v), and 1910.110(b)(9)(vi).

• These minimums are intended to provide a safety margin above normal operating pressures.
• Maintain manufacturer documentation or markings that demonstrate the hose and fittings meet these pressure requirements.

"Listed" means the hose has been evaluated and approved by a recognized testing/listing organization for the stated design, construction, and performance. See 1910.110(b)(9)(iv) and the reference to 1910.110(a)(15).

• In practice, this means the hose should carry a label or documentation showing it is listed to an appropriate standard (manufacturer listing, UL/ANSI listing, or other nationally recognized testing lab).
• Using listed hose helps ensure its materials, construction, and performance (including pressure and temperature ratings) meet OSHA’s expectations for safe LP‑gas service.

For indoor connections, flexible hose must be as short as practical and may not exceed 6 feet (except where 1910.110(c)(5)(i)(g) provides otherwise); it must not extend from one room to another, pass through walls/partitions/ceilings/floors, or be concealed. See 1910.110(b)(9)(vii)(b) and related paragraphs.

• The hose must also be approved for the application and not used where temperatures exceed 125 °F, and rubber slip‑end fittings are not permitted (1910.110(b)(9)(vii)(c)).
• The shutoff valve serving the appliance must be in the metal pipe or tubing upstream of the hose—not at the appliance end (1910.110(b)(9)(vii)(d)).
• Hoses used to connect to wall outlets must also be protected from physical damage (1910.110(b)(9)(vii)(e)).

After installation, piping and tubing must be tested and proved free of leaks using a manometer or equivalent pressure‑indicating device; tests must not be conducted with a flame. See the testing requirement in 1910.110(b)(8)(ix).

• Use a calibrated manometer or equivalent (pressure gauge, electronic sensor) to detect pressure drop rather than soapy‑water/visual flame checks.
• For domestic and commercial systems, perform the specified leak test at not less than normal operating pressures to ensure system integrity.

Piping systems must include provisions to compensate for expansion, contraction, jarring, vibration, and settling; flexible connections are an acceptable way to provide this compensation. See 1910.110(b)(8)(x).

• Typical solutions include flexible connectors, expansion loops, vibration‑isolating supports, and properly designed anchors and guides.
• Plan supports and flexible elements so they do not introduce stress that could cause leakage or damage over time.

Piping located outside buildings may be buried or above ground but must be well supported and protected against physical damage; where soil conditions warrant, buried piping must be protected against corrosion; where condensation may occur, piping must be pitched back to the container or provide a means to revaporize condensate. See 1910.110(b)(8)(xi).

• Corrosion protection can include corrosion‑resistant materials, coatings, wraps, cathodic protection, or tracer wires as appropriate to soil conditions.
• Ensure supports prevent sagging or mechanical damage and that buried piping is installed with proper cover depth and marking to reduce excavation strikes.

Safety relief valves must be spring‑loaded (or equivalent), vent freely to outside air with the discharge at least 5 feet horizontally from any building opening below the discharge, sized to the minimum required flow rate, set to start‑to‑discharge in accordance with Table H‑26, and arranged to minimize tampering. See 1910.110(b)(10)(i), 1910.110(b)(10)(ii), 1910.110(b)(10)(iii), and 1910.110(b)(10)(iv).

• Required flow capacity (CFM of air at standard conditions) is determined from the container or vaporizer surface area using the table/formulas in 1910.110(b)(10)(ii); when the nameplate surface area is unreadable, use the section’s formulas to calculate area.
• Safety relief valves for non‑DOT containers must discharge before pressure exceeds 120% of the maximum permitted start‑to‑discharge setting (1910.110(b)(10)(v)).
• Consider protection from sustained high ambient temperatures (e.g., shading or cooling) to prevent unnecessary valve opening, per 1910.110(b)(10)(vi).