OSHA general industry hazardous materials study guide
Subpart H of OSHA's general industry rules (29 CFR Part 1910) covers hazardous materials. This guide sets out what two of its sections state. 1910.101 sets general requirements for compressed gases, mostly by pointing to DOT regulations and Compressed Gas Association pamphlets, whose content is not summarized here. 1910.106 covers flammable liquids: the definition and the four categories with their flashpoint limits, container and portable tank sizes, storage cabinets, inside storage rooms, incidental use in industrial plants, dispensing, bonding and grounding, sources of ignition and fire control. Tank storage, piping, bulk plants, service stations, processing plants and refineries have further detailed rules not covered here. Consensus standards the rule names (such as NFPA 251 and ASTM test methods) are only named, not summarized. Every point links to the regulation and quotes its exact words.
Compressed gas cylinders
Each employer must determine that the compressed gas cylinders under its control are in a safe condition, to the extent that this can be determined by visual inspection.
“Each employer shall determine that compressed gas cylinders under his control are in a safe condition to the extent that this can be determined by visual inspection.”
Visual and other inspections of cylinders must be done as prescribed in the Department of Transportation Hazardous Materials Regulations (49 CFR parts 171-179 and 14 CFR part 103). Where those regulations are not applicable, the inspections must follow Compressed Gas Association Pamphlets C-6-1968 and C-8-1962, which the rule incorporates by reference.
“Visual and other inspections shall be conducted as prescribed in the Hazardous Materials Regulations of the Department of Transportation (49 CFR parts 171-179 and 14 CFR part 103). Where those regulations are not applicable, visual and other inspections shall be conducted in accordance with Compressed Gas Association Pamphlets C-6-1968 and C-8-1962, which is incorporated by reference as specified in § 1910.6.”
The in-plant handling, storage and use of all compressed gases in cylinders, portable tanks, rail tankcars or motor vehicle cargo tanks must be in accordance with Compressed Gas Association Pamphlet P-1-1965, which the rule incorporates by reference.
“The in-plant handling, storage, and utilization of all compressed gases in cylinders, portable tanks, rail tankcars, or motor vehicle cargo tanks shall be in accordance with Compressed Gas Association Pamphlet P-1-1965, which is incorporated by reference as specified in § 1910.6.”
Compressed gas cylinders, portable tanks and cargo tanks must have pressure relief devices installed and maintained in accordance with Compressed Gas Association Pamphlets S-1.1-1963 (and 1965 addenda) and S-1.2-1963.
“Compressed gas cylinders, portable tanks, and cargo tanks shall have pressure relief devices installed and maintained in accordance with Compressed Gas Association Pamphlets S-1.1-1963 and 1965 addenda and S-1.2-1963”
Not covered here
1910.101 mostly points to DOT regulations and Compressed Gas Association pamphlets. The content of those pamphlets and regulations is not summarized here; read them as the rule incorporates them. We only write what an official source states, so study these parts with your certifying program's materials.
Definitions and categories
Under 1910.106, a flammable liquid is any liquid with a flashpoint at or below 199.4 °F (93 °C). Flammable liquids are divided into four categories.
“Flammable liquid means any liquid having a flashpoint at or below 199.4 °F (93 °C). Flammable liquids are divided into four categories as follows:”
Category 1: flashpoint below 73.4 °F (23 °C) and boiling point at or below 95 °F (35 °C).
“Category 1 shall include liquids having flashpoints below 73.4 °F (23 °C) and having a boiling point at or below 95 °F (35 °C).”
Category 2: flashpoint below 73.4 °F (23 °C) and boiling point above 95 °F (35 °C).
“Category 2 shall include liquids having flashpoints below 73.4 °F (23 °C) and having a boiling point above 95 °F (35 °C).”
Category 3: flashpoint at or above 73.4 °F (23 °C) and at or below 140 °F (60 °C).
“Category 3 shall include liquids having flashpoints at or above 73.4 °F (23 °C) and at or below 140 °F (60 °C).”
When a Category 3 liquid with a flashpoint at or above 100 °F (37.8 °C) is heated for use to within 30 °F (16.7 °C) of its flashpoint, it must be handled under the requirements for a Category 3 liquid with a flashpoint below 100 °F (37.8 °C).
“When a Category 3 liquid with a flashpoint at or above 100 °F (37.8 °C) is heated for use to within 30 °F (16.7 °C) of its flashpoint, it shall be handled in accordance with the requirements for a Category 3 liquid with a flashpoint below 100 °F (37.8 °C).”
Category 4: flashpoint above 140 °F (60 °C) and at or below 199.4 °F (93 °C).
“Category 4 shall include liquids having flashpoints above 140 °F (60 °C) and at or below 199.4 °F (93 °C).”
When a Category 4 flammable liquid is heated for use to within 30 °F (16.7 °C) of its flashpoint, it must be handled under the requirements for a Category 3 liquid with a flashpoint at or above 100 °F (37.8 °C). A liquid with a flashpoint above 199.4 °F (93 °C) heated for use to within 30 °F of its flashpoint must be handled as a Category 4 flammable liquid.
“When a Category 4 flammable liquid is heated for use to within 30 °F (16.7 °C) of its flashpoint, it shall be handled in accordance with the requirements for a Category 3 liquid with a flashpoint at or above 100 °F (37.8 °C). (v) When liquid with a flashpoint greater than 199.4 °F (93 °C) is heated for use to within 30 °F (16.7 °C) of its flashpoint, it shall be handled in accordance with the requirements for a Category 4 flammable liquid.”
Flashpoint is the minimum temperature at which a liquid gives off vapor within a test vessel in enough concentration to form an ignitable mixture with air near the surface of the liquid. The rule names the test methods to use.
“Flashpoint means the minimum temperature at which a liquid gives off vapor within a test vessel in sufficient concentration to form an ignitable mixture with air near the surface of the liquid, and shall be determined as follows:”
A safety can is an approved container of not more than 5 gallons capacity, with a spring-closing lid and spout cover, designed to safely relieve internal pressure when exposed to fire.
“Safety can shall mean an approved container, of not more than 5 gallons capacity, having a spring-closing lid and spout cover and so designed that it will safely relieve internal pressure when subjected to fire exposure.”
A portable tank is a closed container with a liquid capacity over 60 U.S. gallons that is not intended for fixed installation.
“Portable tank shall mean a closed container having a liquid capacity over 60 U.S. gallons and not intended for fixed installation.”
Containers and portable tanks
The container and portable tank storage rules in 1910.106(d) apply only to flammable liquids in drums or other containers (including flammable aerosols) of not more than 60 gallons each, and to portable tanks of not more than 660 gallons each.
“This paragraph shall apply only to the storage of flammable liquids in drums or other containers (including flammable aerosols) not exceeding 60 gallons individual capacity and those portable tanks not exceeding 660 gallons individual capacity.”
Among the listed exceptions, 1910.106(d) does not apply to flammable paints, oils, varnishes and similar mixtures used for painting or maintenance when they are not kept for more than 30 days.
“Flammable paints, oils, varnishes, and similar mixtures used for painting or maintenance when not kept for a period in excess of 30 days;”
Only approved containers and portable tanks may be used. Metal containers and portable tanks that meet, and hold products authorized by, the DOT hazardous materials regulations (49 CFR chapter I) are deemed acceptable.
“Only approved containers and portable tanks shall be used. Metal containers and portable tanks meeting the requirements of and containing products authorized by chapter I, title 49 of the Code of Federal Regulations (regulations issued by the Hazardous Materials Regulations Board, Department of Transportation), shall be deemed to be acceptable.”
Containers must follow Table H-12, except that glass or plastic containers of no more than 1-gallon capacity may be used for a Category 1 or 2 flammable liquid under the conditions listed in 1910.106(d)(2)(iii).
“Flammable liquid containers shall be in accordance with Table H-12, except that glass or plastic containers of no more than 1-gallon capacity may be used for a Category 1 or 2 flammable liquid if:”
Table H-12 (maximum allowable size of containers and portable tanks, Category 1 / 2 / 3 / 4): glass or approved plastic, 1 pt / 1 qt / 1 gal / 1 gal.
“Glass or approved plastic 1 pt 1 qt 1 gal 1 gal.”
Table H-12: metal containers (other than DOT drums), 1 gal for Category 1 and 5 gal for Categories 2, 3 and 4.
“Metal (other than DOT drums) 1 gal 5 gal 5 gal 5 gal.”
Table H-12: safety cans, 2 gal for Category 1 and 5 gal for Categories 2, 3 and 4.
“Safety cans 2 gal 5 gal 5 gal 5 gal.”
Table H-12: metal drums (DOT specifications), 60 gal, and approved portable tanks, 660 gal, for every category.
“Metal drums (DOT specifications) 60 gal 60 gal 60 gal 60 gal. Approved portable tanks 660 gal 660 gal 660 gal 660 gal.”
Not covered here
The other exceptions in 1910.106(d)(1)(ii), the full conditions of the glass or plastic container exception in (d)(2)(iii), and portable tank emergency venting in (d)(2)(ii) are not covered in detail. We only write what an official source states, so study these parts with your certifying program's materials.
Storage cabinets
Not more than 60 gallons of Category 1, 2 or 3 flammable liquids, nor more than 120 gallons of Category 4 flammable liquids, may be stored in a storage cabinet.
“Not more than 60 gallons of Category 1, 2, or 3 flammable liquids, nor more than 120 gallons of Category 4 flammable liquids may be stored in a storage cabinet.”
Storage cabinets must be designed and built to limit the internal temperature to not more than 325 °F when subjected to a 10-minute fire test.
“Storage cabinets shall be designed and constructed to limit the internal temperature to not more than 325 °F. when subjected to a 10-minute fire test”
All joints and seams must stay tight and the door must stay securely closed during the fire test. Cabinets must be labeled in conspicuous lettering: "Flammable—Keep Fire Away."
“All joints and seams shall remain tight and the door shall remain securely closed during the fire test. Cabinets shall be labeled in conspicuous lettering, “Flammable—Keep Fire Away.””
Metal cabinets built this way are deemed to comply: bottom, top, door and sides of at least No. 18 gage sheet iron, double walled with a 1 1/2-inch air space.
“Metal cabinets constructed in the following manner shall be deemed to be in compliance. The bottom, top, door, and sides of cabinet shall be at least No. 18 gage sheet iron and double walled with 11⁄2-inch air space.”
For such a metal cabinet, the door must have a three-point lock and the door sill must be raised at least 2 inches above the bottom of the cabinet.
“The door shall be provided with a three-point lock, and the door sill shall be raised at least 2 inches above the bottom of the cabinet.”
Not covered here
The joint requirements for metal cabinets and the construction of wooden cabinets that are deemed to comply (1910.106(d)(3)(ii)(a) and (b)) are not covered in detail. We only write what an official source states, so study these parts with your certifying program's materials.
Storage rooms and storage areas
Openings from an inside storage room to other rooms or buildings need noncombustible liquid-tight raised sills or ramps at least 4 inches high, or the storage room floor must be at least 4 inches below the surrounding floor; an open-grated trench inside the room that drains to a safe location is a permitted alternative to the sill or ramp. Openings need approved self-closing fire doors, and the room must be liquid-tight where the walls join the floor.
“Openings to other rooms or buildings shall be provided with noncombustible liquid-tight raised sills or ramps at least 4 inches in height, or the floor in the storage area shall be at least 4 inches below the surrounding floor. Openings shall be provided with approved self-closing fire doors. The room shall be liquid-tight where the walls join the floor. A permissible alternate to the sill or ramp is an open-grated trench inside of the room which drains to a safe location.”
Table H-13 (fire protection provided / fire resistance / maximum size / total allowable gallons per sq. ft. of floor area): yes, 2 hours, 500 sq. ft, 10; no, 2 hours, 500 sq. ft, 5; yes, 1 hour, 150 sq. ft, 4; no, 1 hour, 150 sq. ft, 2.
“Yes 2 hours 500 sq. ft 10 No 2 hours 500 sq. ft 5 Yes 1 hour 150 sq. ft 4 No 1 hour 150 sq. ft 2”
Every inside storage room must have either a gravity or a mechanical exhaust ventilation system, designed to give a complete change of air in the room at least six times per hour.
“Every inside storage room shall be provided with either a gravity or a mechanical exhaust ventilation system. Such system shall be designed to provide for a complete change of air within the room at least six times per hour.”
If a mechanical exhaust system is used, it must be controlled by a switch located outside of the door, and the ventilating equipment and any lighting fixtures must be operated by the same switch.
“If a mechanical exhaust system is used, it shall be controlled by a switch located outside of the door. The ventilating equipment and any lighting fixtures shall be operated by the same switch.”
Every inside storage room must keep one clear aisle at least 3 feet wide, and containers over 30 gallons capacity must not be stacked one upon the other.
“In every inside storage room there shall be maintained one clear aisle at least 3 feet wide. Containers over 30 gallons capacity shall not be stacked one upon the other.”
Inside buildings, flammable liquids (including stock for sale) must not be stored so as to limit use of exits, stairways or areas normally used for the safe egress of people.
“Flammable liquids, including stock for sale, shall not be stored so as to limit use of exits, stairways, or areas normally used for the safe egress of people.”
In office occupancies, storage is prohibited except what is required for maintenance and operation of the building and operation of equipment. That storage must be kept in closed metal containers in a storage cabinet, in safety cans, or in an inside storage room without a door opening into the part of the building used by the public.
“Storage shall be prohibited except that which is required for maintenance and operation of building and operation of equipment. Such storage shall be kept in closed metal containers stored in a storage cabinet or in safety cans or in an inside storage room not having a door that opens into that portion of the building used by the public.”
For storage outside buildings, where the quantity stored exceeds 1,100 gallons (or the provisions of subdivision (a) cannot be met), a minimum distance of 10 feet must be kept between buildings and the nearest container of flammable liquid.
“Where quantity stored exceeds 1,100 gallons, or provisions of subdivision (a) of this subdivision cannot be met, a minimum distance of 10 feet between buildings and nearest container of flammable liquid shall be maintained.”
Not covered here
Tables H-14 to H-17 (warehouse and outside storage arrangements) do not appear in the text of the snapshot used here and are not summarized; read them in the regulation. Electrical wiring in storage rooms and the rules for mercantile occupancies and warehouses are not covered in detail. We only write what an official source states, so study these parts with your certifying program's materials.
Incidental use in industrial plants
1910.106(e)(2) applies to the parts of an industrial plant where using and handling flammable liquids is only incidental to the principal business, such as automobile assembly, building electronic equipment or furniture manufacturing.
“This subparagraph shall be applicable to those portions of an industrial plant where the use and handling of flammable liquids is only incidental to the principal business, such as automobile assembly, construction of electronic equipment, furniture manufacturing, or other similar activities.”
In those areas, flammable liquids must be stored in tanks or closed containers.
“Flammable liquids shall be stored in tanks or closed containers.”
Outside an inside storage room or storage cabinet, the quantity in a building or in any one fire area of a building must not exceed 25 gallons of Category 1 liquids in containers, 120 gallons of Category 2, 3 or 4 liquids in containers, or 660 gallons of Category 2, 3 or 4 liquids in a single portable tank.
“The quantity of liquid that may be located outside of an inside storage room or storage cabinet in a building or in any one fire area of a building shall not exceed: (1) 25 gallons of Category 1 flammable liquids in containers (2) 120 gallons of Category 2, 3, or 4 flammable liquids in containers (3) 660 gallons of Category 2, 3, or 4 flammable liquids in a single portable tank.”
At the point of final use, Category 1 or 2 liquids, or Category 3 liquids with a flashpoint below 100 °F (37.8 °C), must be kept in covered containers when not actually in use.
“Category 1 or 2 flammable liquids, or Category 3 flammable liquids with a flashpoint below 100 °F (37.8 °C), shall be kept in covered containers when not actually in use.”
Where flammable liquids are used or handled, except in closed containers, there must be a means to dispose promptly and safely of leakage or spills.
“Where flammable liquids are used or handled, except in closed containers, means shall be provided to dispose promptly and safely of leakage or spills.”
Category 1 or 2 liquids, or Category 3 liquids with a flashpoint below 100 °F (37.8 °C), may be used only where there are no open flames or other sources of ignition within the possible path of vapor travel.
“Category 1 or 2 flammable liquids, or Category 3 flammable liquids with a flashpoint below 100 °F (37.8 °C), may be used only where there are no open flames or other sources of ignition within the possible path of vapor travel.”
Dispensing, bonding and grounding
In industrial plants where use is incidental, flammable liquids may be drawn from or transferred into vessels, containers or portable tanks inside a building only by one of the listed methods: a closed piping system, from safety cans, by a device drawing through the top, or by gravity through an approved self-closing valve.
“Flammable liquids shall be drawn from or transferred into vessels, containers, or portable tanks within a building only through a closed piping system, from safety cans, by means of a device drawing through the top, or from a container or portable tanks by gravity through an approved self-closing valve.”
Transferring by air pressure on the container or portable tank is prohibited.
“Transferring by means of air pressure on the container or portable tanks shall be prohibited.”
In inside storage rooms, dispensing must be by approved pump or self-closing faucet only.
“Dispensing shall be by approved pump or self-closing faucet only.”
In industrial plants, Category 1 or 2 liquids, or Category 3 liquids with a flashpoint below 100 °F (37.8 °C), must not be dispensed into containers unless the nozzle and container are electrically interconnected. A metallic floorplate electrically connected to the fill stem, or a bond wire bonding the fill stem to the container during filling, is deemed to comply.
“Category 1 or 2 flammable liquids, or Category 3 flammable liquids with a flashpoint below 100 °F (37.8 °C), shall not be dispensed into containers unless the nozzle and container are electrically interconnected. Where the metallic floorplate on which the container stands while filling is electrically connected to the fill stem or where the fill stem is bonded to the container during filling operations by means of a bond wire, the provisions of this section shall be deemed to have been complied with.”
At bulk plants, bonding facilities to protect against static sparks must be provided when tank vehicles are loaded through open domes, in the cases the rule lists; one of them is where Category 1 or 2 liquids, or Category 3 liquids with a flashpoint below 100 °F (37.8 °C), are loaded.
“Bonding facilities for protection against static sparks during the loading of tank vehicles through open domes shall be provided: (1) Where Category 1 or 2 flammable liquids, or Category 3 flammable liquids with a flashpoint below 100 °F (37.8 °C), are loaded, or”
That bonding connection must be made fast to the vehicle or tank before dome covers are raised, and must stay in place until filling is completed and all dome covers have been closed and secured.
“Such bonding connection shall be made fast to the vehicle or tank before dome covers are raised and shall remain in place until filling is completed and all dome covers have been closed and secured.”
At service stations, Category 1 or 2 liquids, or Category 3 liquids with a flashpoint below 100 °F (37.8 °C), must not be delivered into portable containers unless the container is metal, has a tight closure with screwed or spring cover, and has a spout or is designed so the contents can be poured without spilling.
“No delivery of any Category 1 or 2 flammable liquids, or Category 3 flammable liquids with a flashpoint below 100 °F (37.8 °C), shall be made into portable containers unless the container is constructed of metal, has a tight closure with screwed or spring cover, and is fitted with a spout or so designed so the contents can be poured without spilling.”
Not covered here
The exceptions to tank vehicle bonding in 1910.106(f)(3)(iv)(d), tank car stray current protection, and the dispensing system rules for service stations and marine service stations are not covered in detail. We only write what an official source states, so study these parts with your certifying program's materials.
Sources of ignition and fire control
In industrial plants, adequate precautions must be taken to prevent the ignition of flammable vapors. Sources of ignition include, but are not limited to, open flames, lightning, smoking, cutting and welding, hot surfaces, frictional heat, static, electrical and mechanical sparks, spontaneous ignition (including heat-producing chemical reactions) and radiant heat.
“Adequate precautions shall be taken to prevent the ignition of flammable vapors. Sources of ignition include but are not limited to open flames; lightning; smoking; cutting and welding; hot surfaces; frictional heat; static, electrical, and mechanical sparks; spontaneous ignition, including heat-producing chemical reactions; and radiant heat.”
Open flames and smoking are not permitted in flammable liquid storage areas.
“Open flames and smoking shall not be permitted in flammable liquid storage areas.”
In industrial plants, hot work (such as welding or cutting, use of spark-producing power tools, and chipping) is permitted only under the supervision of an individual in responsible charge, who must inspect the area to be sure it is safe for the work and that safe procedures will be followed.
“Hot work, such as welding or cutting operations, use of spark-producing power tools, and chipping operations shall be permitted only under supervision of an individual in responsible charge. The individual in responsible charge shall make an inspection of the area to be sure that it is safe for the work to be done and that safe procedures will be followed for the work specified.”
At least one portable fire extinguisher rated not less than 12-B units must be located outside of, but not more than 10 feet from, the door opening into any room used for storage.
“At least one portable fire extinguisher having a rating of not less than 12-B units shall be located outside of, but not more than 10 feet from, the door opening into any room used for storage.”
At least one portable fire extinguisher rated not less than 12-B units must be located not less than 10 feet, nor more than 25 feet, from any Category 1, 2 or 3 flammable liquid storage area that is outside a storage room but inside a building.
“At least one portable fire extinguisher having a rating of not less than 12-B units must be located not less than 10 feet, nor more than 25 feet, from any Category 1, 2, or 3 flammable liquid storage area located outside of a storage room but inside a building.”
Materials that react with water must not be stored in the same room with flammable liquids.
“Materials which will react with water shall not be stored in the same room with flammable liquids.”
In industrial plants, combustible waste material and residues in a building or unit operating area must be kept to a minimum, stored in covered metal receptacles and disposed of daily.
“Combustible waste material and residues in a building or unit operating area shall be kept to a minimum, stored in covered metal receptacles and disposed of daily.”
Not covered here
Fire control and ignition rules for tank storage, bulk plants, service stations, processing plants and refineries are not covered in detail. We only write what an official source states, so study these parts with your certifying program's materials.
Sources
- eCFR: 29 CFR 1910.101, Compressed gases (general requirements) (as of Nov 3, 2026)Checked November 5, 2026
- eCFR: 29 CFR 1910.106, Flammable liquids (as of Nov 3, 2026)Checked November 5, 2026
Other OSHA General Industry study guides: Walking-working surfaces, Exit routes and emergency planning, Fire protection, Electrical safety, Personal protective equipment, Permit-required confined spaces, Lockout/tagout, Machine guarding, Welding, cutting and brazing, Electric power generation, transmission and distribution, Powered industrial trucks (forklifts), Materials handling and storage, Bloodborne pathogens, Occupational noise exposure