Flammable liquids requirements

You must use approved safety cans or Department of Transportation approved containers for handling flammable liquids in quantities of 5 gallons or less; for quantities of one gallon or less you may use the original container. See 1926.152(a)(1).

• Use approved safety cans or DOT-approved containers for up to 5 gallons.
• Original shipping containers may be used for highly viscid materials or for quantities of 1 gallon or less.

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No — flammable liquids must not be stored in areas used for exits, stairways, or normally used for the safe passage of people. See 1926.152(a)(2).

• Keep storage out of egress paths to preserve safe evacuation routes.

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You may store no more than 25 gallons of flammable liquids in a room outside of an approved storage cabinet. See 1926.152(b)(1).

• Quantities above 25 gallons must be in approved cabinets or storage rooms as required by the standard.

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Cabinets must be either approved metal cabinets or constructed of specified 1-inch exterior-grade plywood with fire-retardant paint and secure joints, and they must be labeled "Flammable-Keep Away from Open Flames." See 1926.152(b)(2)(i), 1926.152(b)(2)(ii), and 1926.152(b)(2)(iii).

• Wooden cabinets: 1" exterior-grade plywood, rabbeted joints, properly fastened, steel hinges mounted to resist burning out, painted with fire-retardant paint.
• Metal cabinets: must be an approved design.
• All cabinets must be labeled in conspicuous lettering: "Flammable-Keep Away from Open Flames."

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A single storage cabinet may contain not more than 60 gallons of Category 1, 2, and/or 3 flammable liquids, or 120 gallons of Category 4 flammable liquids. See 1926.152(b)(3).

• Do not exceed these cabinet capacity limits to remain compliant.

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You may have up to three storage cabinets in a single storage area; quantities in excess of that must be stored in an inside storage room. See 1926.152(b)(4).

• If you need more than three cabinets in the same area, use a properly constructed inside storage room meeting the standard's requirements.

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Inside storage rooms must meet the required fire-resistive rating per NFPA 251-1969 test specifications appropriate for their use. See 1926.152(b)(4)(i).

• Follow the referenced Standard Methods of Fire Test of Building Construction and Material, NFPA 251-1969, for construction details and ratings.

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When an automatic extinguishing system is provided, openings to other rooms must have liquid-tight raised sills or ramps at least 4 inches high or the storage room floor must be at least 4 inches below surrounding floors, and openings must have approved self-closing fire doors; room floors and walls must be liquid-tight where they join. See 1926.152(b)(4)(ii).

• An open-grated trench draining to a safe location is an acceptable alternative to a sill or ramp.
• Windows and exposed openings must be protected per NFPA No. 80-1970 for Class E or F openings when other building portions are exposed.

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No — materials that will react with water and create a fire hazard must not be stored in the same room with flammable liquids. See 1926.152(b)(4)(iii).

• Keep such reactive materials in separate, appropriate storage to avoid hazardous reactions.

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The allowable gallons per square foot depend on fire protection and required fire-resistance rating as shown in Table F-2: for example, with a 2-hour fire resistance and sprinklered protection you may store 10 gallons per sq. ft. up to 500 sq. ft; without fire protection the limit is 4 gallons per sq. ft. See 1926.152(b)(4)(iv).

• Table F-2 gives combinations of fire resistance, maximum room size, and total allowable gallons per sq. ft. (e.g., 2 hrs with protection = 10 gals/sq. ft. up to 500 sq. ft.).
• The fire protection system must be approved (sprinkler, water spray, CO2, or other nationally recognized testing laboratory approved system).

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Electrical wiring and equipment in inside storage rooms must be approved for Class I, Division 1 hazardous locations, and the room must have gravity or mechanical exhaust that starts not more than 12 inches above the floor and provides at least six air changes per hour; mechanical systems must be controlled by a switch outside the door and the ventilating equipment and lighting must operate on the same switch. See 1926.152(b)(4)(v) and 1926.152(b)(4)(vi).

• Ventilation intake and exhaust must be properly located and controlled to remove vapors.
• Use approved electrical equipment rated for Class I, Division 1 areas.

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Inside storage rooms must have at least one clear aisle at least 3 feet wide, and containers over 30 gallons must not be stacked; any flammable liquids in excess of room permitted amounts must be stored outside in accordance with paragraph (c). See 1926.152(b)(4)(vii) and 1926.152(b)(4)(viii).

• Maintain the 3-foot aisle for safe access and operation.
• Do not stack containers over 30 gallons to prevent instability and spill risk.

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The quantity of flammable liquids near spraying operations must be the minimum required for operations and ordinarily should not exceed a supply for one day or one shift; bulk storage of portable containers must be in a separate detached building or cut off in a standard manner. See 1926.152(b)(5).

• Keep only the minimal working supply near spraying to reduce fire risk.
• Store bulk portable containers separately from important buildings.

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Outdoor storage of containers (each not more than 60 gallons) shall not exceed 1,100 gallons in any one pile or area; piles or groups of containers must be separated by a 5-foot clearance and must be at least 20 feet from a building. See 1926.152(c)(1).

• Max 1,100 gallons per pile/area for portable containers ≤60 gal each.
• Maintain 5-foot gaps between groups and 20-foot minimum distance to buildings.

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Within 200 feet of each pile there must be a 12-foot-wide access way for fire control apparatus, and the storage area must be graded or surrounded by a curb or dike at least 12 inches high to divert spills away from buildings; drains must lead to a safe location and be operable under fire conditions. See 1926.152(c)(2) and 1926.152(c)(3).

• Provide the 12-foot emergency access lane within 200 feet of storage.
• Control spills by grading, curbs, or trenches; ensure drains terminate safely and are accessible during fires.

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Portable tanks must be at least 20 feet from any building; groups of tanks with combined capacity over 2,200 gallons must be separated by a 5-foot clear area, and individual tanks over 1,100 gallons must be separated by 5 feet; within 200 feet of each portable tank there must be a 12-foot-wide access way for fire control apparatus. See 1926.152(c)(4)(i) and 1926.152(c)(4)(ii).

• Maintain 20-foot setback to buildings and required 5-foot separations for grouped tanks.
• Provide a 12-foot emergency access way within 200 feet of tanks.

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Portable tanks not exceeding 660 gallons must have emergency venting and other devices as required by chapters III and IV of NFPA 30-1969, and tanks over 660 gallons must have emergency venting and devices as required by chapters II and III of NFPA 30-1969. See 1926.152(c)(6) and 1926.152(c)(7).

• Follow the specified chapters of NFPA 30-1969 for required venting and safety devices depending on tank size.

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You must have at least one portable fire extinguisher with a rating of not less than 20-B units located outside but within 10 feet of the door to any room used for storage of more than 60 gallons, and at least one 20-B unit extinguisher located 25–75 feet from any outdoor storage area; tank trucks and vehicles used for transporting or dispensing flammable liquids must carry at least a 20-B:C unit extinguisher. See 1926.152(d)(1), 1926.152(d)(2), and 1926.152(d)(4).

• Ensure portable extinguishers of the specified rating are positioned for quick access as described.
• When sprinklers are provided, they must be installed per NFPA 13-1969. See 1926.152(d)(3).

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Areas where more than 5 gallons are transferred at one time must be separated from other operations by 25 feet or by construction having at least 1-hour fire resistance, must provide drainage or other means to control spills, and must have adequate natural or mechanical ventilation to keep flammable vapor concentrations at or below 10 percent of the lower flammable limit. See 1926.152(e)(1).

• Maintain the 25-foot separation or 1-hour-rated construction.
• Provide spill controls and ventilation designed to maintain vapors ≤10% LFL.

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Transfer of Category 1, 2, or 3 flammable liquids from one container to another must be done only when the containers are electrically interconnected (bonded). See 1926.152(e)(2).

• Bonding prevents static discharge and reduces the risk of ignition during transfer of these categories.

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Flammable liquids may only be drawn or transferred through a closed piping system, from safety cans, by devices drawing through the top, or by gravity or pump through an approved self-closing valve; transferring by means of air pressure on the container or portable tanks is prohibited. See 1926.152(e)(3).

• Allowed: closed piping, safety cans, top-draw devices, gravity or pump with approved self-closing valves.
• Prohibited: using air pressure to transfer liquids from containers or portable tanks.

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Category 1, 2, or 3 flammable liquids must be kept in closed containers when not actually in use, and dispensing devices/nozzles must be of an approved type. See 1926.152(e)(5) and 1926.152(f)(1).

• Keep these liquids closed when not in use to limit vapors and spills.
• Use approved dispensing equipment and nozzles for these categories.

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Leakage or spillage of flammable liquids must be disposed of promptly and safely, and Category 1, 2, or 3 flammable liquids may be used only where there are no open flames or other sources of ignition within 50 feet of the operation unless a greater clearance is necessary. See 1926.152(f)(2) and 1926.152(f)(3).

• Clean up spills quickly and safely to reduce fire/explosion risk.
• Maintain at least a 50-foot clearance from open flames or ignition sources for these categories.

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Service and refueling areas must store flammable liquids in approved closed containers, underground tanks, or aboveground portable tanks; tank trucks must meet NFPA 385-1966; dispensing hoses must be approved, nozzles must be approved automatic-closing types without latch-open devices, and underground tanks must not be abandoned. See 1926.152(g)(1), 1926.152(g)(2), 1926.152(g)(3), 1926.152(g)(4), and 1926.152(g)(5).

• Use approved equipment for storage and dispensing and comply with referenced NFPA standards for tank vehicles.

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Service and fueling areas must have clearly identified remote switches to shut off power to dispensing devices, approved heating placement and types depending on dispensing activities, no smoking or open flames with conspicuous signs prohibiting smoking, motors turned off during fueling, and at least one 20-B:C fire extinguisher within 75 feet of pumps, dispensers, underground fill openings and service areas. See 1926.152(g)(6) through 1926.152(g)(11).

• Provide remote emergency shutoff switches.
• Install heating equipment per the height and approved-type rules based on whether dispensing occurs.
• Prohibit smoking and post clear signs.
• Require motors to be shut off during fueling.
• Provide required fire extinguishers within specified distances.

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Dispensing units must be protected against collision damage. See 1926.152(e)(4).

• Provide physical barriers or other means to prevent vehicles or equipment from striking dispensing units.

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Storage areas must be kept free of weeds, debris, and other combustible material not necessary to the storage. See 1926.152(c)(5).

• Regularly remove unnecessary combustible materials to reduce fire risk around storage piles or tanks.

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To reduce ignition and static risks, bond containers when transferring Category 1–3 flammable liquids, use closed piping or approved self-closing valves and approved dispensing devices (no air-pressure transfer), and keep Category 1–3 liquids in closed containers when not in use. See 1926.152(e)(2), 1926.152(e)(3), 1926.152(e)(5), and 1926.152(f)(1).

• Bonding prevents static sparks during transfers of certain categories.
• Use approved closed systems and self-closing valves; do not pressurize containers with air to transfer.
• Keep containers closed when not actively using the liquid.

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Heating equipment installed where Category 1, 2, or 3 flammable liquids are dispensed must be of an approved type for garages and must be installed at least 8 feet above the floor. See 1926.152(g)(7)(ii).

• If there is no dispensing or transferring of Category 1–3 liquids, approved heating may be installed with the bottom at least 18 inches above the floor; different rules apply when dispensing occurs.

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Category 1, 2, or 3 flammable liquids may be used only where there are no open flames or other sources of ignition within 50 feet of the operation, unless conditions require a greater clearance. See 1926.152(f)(3) and note that transfer areas with >5 gallons must also meet the separation or 1-hour construction requirement in 1926.152(e)(1).

• Maintain at least a 50-foot no-ignition zone around use of these flammable liquids.

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Yes — aggregate quantities of hazardous flammable materials on site in one location can bring other standards into play: for flammable gases and certain flammable liquids, large aggregate amounts at one location can trigger Process Safety Management coverage under 29 CFR 1910.119, as explained in OSHA's interpretation about flammable gas aggregation. See 1926.152(c) and the OSHA letter on PSM flammable gas aggregation at https://www.osha.gov/laws-regs/standardinterpretations/2024-06-06.

• If aggregate on-site amounts of a covered highly hazardous chemical meet or exceed the threshold for another standard (for example, PSM), employers must comply with that standard in addition to the flammable liquids storage rules.

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Dispensing devices and nozzles for Category 1, 2, or 3 flammable liquids must be of an approved type; hoses must be approved, and nozzles must be automatic-closing types without latch-open devices. See 1926.152(e)(5) and 1926.152(g)(3) and 1926.152(g)(4).

• Use approved hoses and automatic-closing nozzles without latch-open mechanisms to prevent unattended flow and reduce spill/ignition risks.

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Sprinklers must be installed in accordance with NFPA 13-1969, and approved fire protection systems acceptable for Table F-2 include sprinkler, water spray, carbon dioxide, or other systems approved by a nationally recognized testing laboratory. See 1926.152(d)(3) and 1926.152(b)(4)(iv).

• Follow NFPA 13-1969 for sprinkler system design and installation.
• Use only systems approved by nationally recognized testing laboratories for the purposes described in the standard.

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To prevent spills from reaching buildings you may grade the area to divert spills away or surround it with a curb or earth dike at least 12 inches high (with drains terminating to a safe location); alternatively, an open-grated trench inside the room that drains to a safe location is allowed for indoor storage; and within 200 feet of each pile or portable tank there must be a 12-foot-wide access way for fire control apparatus. See 1926.152(c)(3) and 1926.152(c)(4)(ii).

• Provide grading, curbs/dikes, or trenches to control spills; ensure drains are accessible under fire conditions.
• Keep a 12-foot access way within 200 feet for emergency responders.

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If a mechanical exhausting system is used, its switch must be located outside of the storage room door, and there must be at least one clear aisle at least 3 feet wide in every inside storage room. See 1926.152(b)(4)(vi) and 1926.152(b)(4)(vii).

• Place controls for ventilation outside the room to avoid entering a hazard area to start ventilation.
• Maintain a 3-foot clear aisle for safe movement and access.

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This section covers flammable liquids with a flashpoint at or below 199.4 ºF (93 ºC). See Scope in 1926.152(h).

• The rule applies to the handling, storage, and use of those flammable liquids.
• It expressly does not apply to bulk transportation of flammable liquids (1926.152(h)(1)) or to storage/handling/use of fuel oil tanks and containers connected with oil-burning equipment (1926.152(h)(2)).

If you handle liquids with higher flashpoints or perform bulk transport or fuel-oil-equipped tank work, other standards or exemptions may apply.

Tanks shall be built of steel, but there are specified exceptions for underground tanks or where the liquid’s properties require other materials; aboveground or indoor tanks must be noncombustible. See Materials in 1926.152(i)(1)(i).

• General rule: tanks shall be built of steel.
• Exception: tanks may be built of other materials for underground installation or when required by the stored liquid’s properties (1926.152(i)(1)(i)(B)).
• Aboveground or inside-building tanks: must be of noncombustible construction.

If you plan to use non-steel materials, make sure the design follows recognized engineering practice as required by 1926.152(i)(1)(i)(C).

Unlined concrete tanks may be used only for storing flammable liquids that have a gravity of 40° API or heavier. See 1926.152(i)(1)(i)(D).

• "40° API or heavier" means heavier (higher specific gravity) petroleum products; lighter distillates are not covered by this allowance.
• If you plan to use concrete for other flammable liquids, you must use concrete with special lining and follow sound engineering practice as noted in adjacent provisions.

Special engineering consideration is required if the liquid’s specific gravity exceeds that of water or if tanks are designed to contain flammable liquids at temperatures below 0 °F. See 1926.152(i)(1)(i)(F).

• This means you must account for unusual loads, stresses, material selection, and corrosion allowances when designing tanks under those conditions.
• Use qualified engineers to document design changes and any extra thickness, coatings, or linings needed per the standard.

Metal tanks may be welded, riveted, caulked, brazed, or bolted, or made using combinations of those methods, and brazing filler metal must be nonferrous or an alloy with a melting point above 1000 °F and below the metal joined. See 1926.152(i)(1)(ii)(B).

• Acceptable construction methods include welding, riveting, caulking, brazing, and bolting.
• If brazing is used, the filler metal must be nonferrous or an alloy melting above 1000 °F but below the base metal’s melting point.
• Ensure fabrication meets applicable codes or accepted industry standards referenced elsewhere in the section.

Atmospheric tanks must be built in accordance with acceptable good standards of design and may be built to specified Underwriters' Laboratories or American Petroleum Institute standards. See Atmospheric tanks in 1926.152(i)(1)(iii)(A) and the UL reference at 1926.152(i)(1)(iii)(A)(1).

• Examples listed include Underwriters' Laboratories Subjects No. 142, No. 58, or No. 80 and various API standards cited in the same subsection.
• Tanks built to those consensus standards are acceptable provided the chosen standard matches the tank type and service.

Always document which standard you used and ensure the tank is suitable for the stored liquid and operating conditions.

Tanks designed for underground service and not exceeding 2,500 gallons may be used aboveground, but atmospheric tanks shall not be used to store a flammable liquid at or above its boiling point. See 1926.152(i)(1)(iii)(B) and 1926.152(i)(1)(iii)(D).

• If you plan to place an underground-rated tank above ground, confirm it is 2,500 gallons or smaller and suitable for aboveground service per the standard.
• Never store a flammable liquid in an atmospheric tank at temperatures that reach or exceed the liquid’s boiling point—use pressure-rated vessels if that condition is expected.

Low-pressure tanks must be built to acceptable design standards and their normal operating pressure must not exceed the tank’s design pressure. See 1926.152(i)(1)(iv)(A) and (B).

• The standard allows low-pressure tanks to be built to recognized standards such as API 620 or other accepted codes (1926.152(i)(1)(iv)(B)(1)-(2)).
• Atmospheric tanks built according to UL requirements are limited to 2.5 psig under emergency venting conditions and the paragraph may be used for operating pressures not exceeding 1 psig (1926.152(i)(1)(iv)(C)).

Make sure the chosen standard and pressure ratings match your service conditions and that the tank is tested and documented accordingly.

Pressure vessels must be built according to the ASME Code for Unfired Pressure Vessels (Section VIII) and their normal operating pressure must not exceed the vessel’s design pressure. See 1926.152(i)(1)(v)(A) and (B).

• Design and construction must follow Section VIII of the ASME Boiler and Pressure Vessel Code, 1968, or an equivalent accepted code.
• Never operate a pressure vessel above its certified design pressure; provide appropriate relief and safety devices as required by the applicable code.

The distance between any two flammable liquid storage tanks must be at least 3 feet, and in many cases must be not less than one-sixth the sum of their diameters unless an exception applies. See 1926.152(i)(2)(ii)(A) and (B).

• Minimum always: 3 feet between any two tanks (1926.152(i)(2)(ii)(A)).
• Additional rule: distance between adjacent tanks shall not be less than one-sixth the sum of their diameters, except where other exceptions apply (1926.152(i)(2)(ii)(B)).
• If one tank’s diameter is less than half the adjacent tank’s diameter, spacing may be one-half the smaller tank’s diameter under that paragraph.

Check for specific exceptions like small-capacity crude oil tanks in noncongested areas in 1926.152(i)(2)(ii)(C).

Unstable flammable liquids require greater spacing, compacted or multi-row tank arrangements must allow firefighting access, and minimum separation from LPG containers has specific distances. See 1926.152(i)(2)(ii)(D)-(F).

• Unstable liquids: distance between tanks must be at least one-half the sum of their diameters (1926.152(i)(2)(ii)(D)).
• Compacted rows/irregular patterns: provide greater spacing or other means so inside tanks remain accessible for firefighting (1926.152(i)(2)(ii)(E)).
• LPG containers: minimum separation from a flammable liquid tank is 20 feet, with some exceptions for small tanks and diked areas described in the paragraph (1926.152(i)(2)(ii)(F)).

Design tank layouts to meet these spacing rules and to ensure emergency access for firefighting and spill control.

Normal vents must be sized according to an accepted standard such as API Standard 2000 or be at least as large as the larger of the filling or withdrawal connection, but never less than 1¼ inches inside diameter. See 1926.152(i)(2)(iv)(B) and (B)(1)-(3).

• Preferred sizing methods include API 2000 (1968) or another accepted standard (1926.152(i)(2)(iv)(B)(1)-(2)).
• If no standard is used, the vent must be at least as large as the filling or withdrawal connection, whichever is larger, and never less than 1.25 in ID (1926.152(i)(2)(iv)(B)(3)).

Always document vent sizing calculations or the accepted standard you used to determine vent size.

Vents and vent drains must be arranged to prevent localized overheating if vented vapors could be ignited unless the vent is designed to limit internal pressure to 2.5 psig or less; tanks storing Category 1 (and many Category 2/3) flammable liquids must have normally-closed vents or approved flame arresters, with limited exemptions. See 1926.152(i)(2)(iv)(E)-(G).

• If vents are not pressure-limited to 2.5 psig, arrange vent outlets to avoid localized overheating if vapors ignite (1926.152(i)(2)(iv)(E)).
• Tanks storing Category 1 flammable liquids must use venting devices that are normally closed except when venting under pressure or vacuum; Category 2 or some Category 3 tanks generally require normally-closed vents or approved flame arresters (1926.152(i)(2)(iv)(F)).
• There are limited exemptions (e.g., certain small crude oil tanks or outside aboveground tanks under 1,000 gallons for non-Category 1 liquids) and an allowance to omit flame arresters where their obstruction could result in tank damage (1926.152(i)(2)(iv)(F)-(G)).

If you rely on an exemption, document the basis and ensure safe venting to protect the tank and nearby equipment.

Every aboveground storage tank must have construction or devices that relieve excessive internal pressure caused by exposure fires, and total venting capacity (normal plus emergency) must meet the values derived from Table F-10 unless another paragraph provides an exception. See 1926.152(i)(2)(v) and (i)(2)(v)(A)-(C).

• Tanks must have some form of emergency pressure relief (floating roof, lifter roof, weak roof-to-shell seam, or approved pressure-relieving construction) (1926.152(i)(2)(v)(A)-(B)).
• If relief devices provide the only emergency relief, combined normal plus emergency vent capacity must be sufficient to prevent shell or bottom rupture under fire exposure; calculation methods reference Table F-10 and wetted-area assumptions (1926.152(i)(2)(v)(C)).
• The standard specifies methods for calculating wetted area and refers to Table F-10 for required free-air venting capacity.

Document your emergency venting design, sizing method, and any exceptions relied upon to demonstrate compliance with the venting capacity requirements.

Vent pipe outlets must discharge outside and be located at least 12 feet above adjacent ground level, and they must be arranged to disperse vapors upward or horizontally away from nearby walls so vapors do not enter buildings or get trapped.

• Required height and discharge direction: Vent outlets for tanks storing Category 1 or 2 flammable liquids (and Category 3 with flashpoint below 100 °F) that are adjacent to buildings or public ways must be located so vapors are released at a safe point outside and not less than 12 feet (3.658 m) above the adjacent ground level, and vapors should be discharged upward or horizontally away from closely adjacent walls (1926.152(i)(2)(vi)(B)).
• Keep vapors from re-entering buildings: Vent outlets must be positioned so flammable vapors will not be trapped by eaves or other obstructions and must be at least 5 feet (1.52 m) from building openings (1926.152(i)(2)(vi)(B)).
• Manifolded vents: If multiple tanks are manifolded together, pipe sizes must be sufficient to discharge the vapors they may be required to handle under fire exposure, within the system’s pressure limits (1926.152(i)(2)(vi)(C)).

Follow these placement rules to reduce risk of vapor accumulation near buildings and public ways and to comply with the venting requirements in 1926.152(i)(2)(vi)(B).