OSHA Outreach Safety Training

General Industry Safety Standards

Hazardous Materials

Subpart H

Flammable and Combustible Liquids

29 CFR 1910.106

Introduction:

The Primary basis of this standard is the National Fire Protection Association's publication NFPA 30, Flammable and Combustible Liquids Code.

This standard applies to the handling, storage, and use of flammable and combustible liquids with a flash point below 200º F. There are two primary hazards associated with flammable and combustible liquids:

          A:      Fires

          B:      Explosions

In order to prevent these hazards, this standard addresses the primary concerns of: design and construction, ventilation, ignition sources, and storage.

Definitions:

1- Boiling Point:

Shall mean the boiling point of a liquid at a pressure of 14.7 pounds per square inch absolute (psia).

2- Flash Point

Means the minimum temperature at which a liquid gives off vapor in sufficient concentration to from an ignitable mixture with air near the surface of the liquid.

3- Combustible Liquids:

Means any liquid having a flash point at or above 100º F (37.8º C).

4- Flammable Liquids:

Means any liquid having a flash point below 100º F (37.8º C).

5- Portable Tank:

Shall mean a closed container having a liquid capacity over 60 US gallons and not intended for fixed installation.

6- 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.

7- Vapor Pressure:

Shall mean the pressure, measured in pounds per square inch (absolute) exerted by volatile liquid.

Vapor pressure is a measure of liquid's propensity to evaporate. The higher the vapor pressure, the more volatile the liquid and, thus the more readily the liquid gives off vapors.

8- Ventilation:

Ventilation as specified in this section is for the prevention of fire and explosion. It is considered adequate if it is sufficient to prevent accumulation of significant quantities of vapor-air mixtures in concentration over one-fourth of the lower flammable limit.

9- Closed Container:

Shall mean a container so sealed by means of a lid or other device that neither liquid nor vapor will escape from it at ordinary temperature.

Flammable (Explosive) Limits:

When vapors of a flammable or combustible liquid are mixed with air in the proper proportions in the presence of a source of ignition, rapid combustion or an explosion can occur.

The proper proportion is called the Flammable Range and is often referred to as the Explosive Range. The flammable range includes all concentrations of flammable vapor or gas in air, in which a flash will occur or a flame will travel if the mixture is ignited.

There is a minimum concentration of vapor or gas in air below which propagation of flame does not occur on contact with a source of ignition {Lower Flammable Limits (LFL) or Lower Explosive Limits (LEL)} There is also a maximum proportion of vapor in air above which propagation of flame does not occur { (UFL) or (UEL) }.

These boundary - line mixtures of vapor with air are usually expressed in terms of percentage by volume in air.

When the difference between the lower limits and the upper limits (Flammability Range) is large, the substance is considered dangerous.

For Example: The lower Flammability limit of motor gasoline is 1.6 % and the upper limit is 7%, while the lower limit of acetylene is 1.5% and the upper limit is 82%, in this case acetylene is considered very much dangerous than motor gasoline.

Table 1 shows some typical limits of flammability of some substances.

Table 1

Classification of Flammable and Combustible Liquids:

Flammable and Combustible liquids are classified as follows:

A- Flammable Liquids:

Flammable liquids shall be known as Class I liquids. Class I liquids are divided into three classes as follows:

Class IA:

Shall include liquids having flash points below 73ºF (22.8º C) and having boiling point below 100º F (37.8º C).

Examples: Acetaldehyde, Ethylamine, Ethyl Ether, Ethylene Oxide, Methyl Chloride.

Class IB:

Shall include liquids having flash points below 73ºF (22.8º C) and having a boiling point at or above 100º F (37.8º C).

Examples: Acetone, Acetonitrile, Benzene, Cyclohexane, Isooctane, Methyl Alcohol.

Class IC:

Shall include liquids having flash points at or above 73ºF (22.8º C) and below 100º F (37.8º C).

Examples: Chloro-Benzene, Amyl Alcohol, Di-Butyl Ether, Methyl Butyl Ketone, Isobutyl Alcohol.

B- Combustible Liquids:

Combustible Liquids shall be divided into two classes as follows:

Class II Liquids:

Shall include those with flash points at or above 100º F (37.8º C) and below 140º F (60º C) .

Examples: Di-Butyl Amine, Hexyl Alcohol, Hydrazine, 3- pentanol, .

Class III Liquids:

Shall include those with flash points at or above 140º F (60º C) , Class III liquids are subdivided into two subclasses:

          Class III A:

Shall include those liquids with flash points at or above 140º F (60º C) and below 200º F (93.3º C).

Examples: Naphthalene, Formaldehyde 37%, 2-Heptanol, Nitrobenzene.

Class III B:

Shall include those with flash points at or above 200º F (93.3º C).

Examples: Benzyl Alcohol, Diethyl Sulfate, Glycerine, Methylene Chloride.

Container and Portable Tank Storage:

1-     Only approved containers and portable tanks may be used to store flammable and combustible liquids. (DOT).

2-     Portable tanks should have provision for emergency venting. Top mounted emergency vents must be capable of limiting internal pressure under fire exposure conditions to 10 psig or 30 % of bursting pressure of the tank, whichever is greater.

3-     Portable tanks are also required to have at least one pressure - activated vent with a minimum capacity of 6000 cubic feet of free air at 14.7 psia and 60ºF. These vents must be set to open at not less than 5 psig. If fusible vents are used, they shall be actuated by elements that operate at a temperature not exceeding 300º F.

4-     Maximum allowable sizes of various types of containers and portable tanks are specified based on the class of flammable and combustible liquid they contain.

a-Design , Construction and Capacity of Storage Cabinets:

1-     Not more than 60 gallons of Class I / or Class II liquids, or not more than 120 gallons of Class III liquids may be stored in an individual cabinet.

2-     Storage cabinets shall be designed and constructed to limit the internal temperature to not more than 325º F when subjected to a standardized 10-minute fire test.

3-     All joints and seams shall remain tight and the door shall remain securely closed during the fire test.

4-     Storage cabinets shall be conspicuously labeled, "Flammable - Keep Fire Away."

5-     The bottom, top, door, and sides of metal cabinets shall be at least No. 18 gage sheet metal and double walled with 1.5-inch air space. 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.

b- Design and Construction of Inside Storage Rooms:

1-                 Openings to other rooms or buildings shall be provided with non-combustible 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.

2-                 A permissible alternate to the sill or ramp is an open - grated trench inside of the room which drains to a safe location.

3-                 Electrical wiring and equipment located in inside storage rooms used for Class I liquids shall be approved under Subpart S Electrical, for Class I, Division 2 Hazardous Locations. For Class II and Class III liquids, shall be approved for general use.

4-                 Rating and capacity: Storage in inside storage rooms shall comply with the following:

5-       Ventilation:

Every inside storage room shall be provided with either a gravity or a mechanical exhaust ventilation system designed to provide for a complete change of air within the room at least six (6) times per hour. (1 cubic feet per minute for each ft² of floor area)

6-       In every inside storage room, there shall be maintained an aisle at least 3 feet wide.

7-       Containers over 30 gallons capacity shall not be stacked one upon the other.

8-       Dispensing shall be only by approved pump or self-closing faucet.

c- Warehouses or Storage Buildings:

1-                 Practically any quantity of flammable and combustible liquid can be stored in these buildings provided that they are stored in configuration consistent with table 1.

2-                 Containers in piles shall be separated by pallets to provide stability and to prevent excessive stress on containers walls.

3-                 Stored materials shall not be piled within 3 feet of beams or girders and shall be at least 3 feet below sprinkler deflectors or other fire protection equipment.

4-                 Aisles of at least 3 feet in width shall be maintained to access doors, windows or standpipe connections.

d- Storage Outside Buildings:

1-                 Suitable fire control devices, such as small hose, portable fire extinguishers, shall be available at locations where flammable or combustible are stored.

2-                 Open flames and smoking shall not be permitted in flammable or combustible liquid storage areas.

3-                 Materials which react with water shall not be stored in the same room with flammable or combustible liquids.

Industrial Plants:

a- Incidental Storage or Use of Flammable or Combustible Liquids:

This subparagraph is applicable to those portions of an industrial plant where the use and handling of flammable or combustible liquids is only incidental to the principal business, such as paint thinner storage in an automobile assembly plant, solvents used in the construction of electronic equipment, and flammable finishing materials used in furniture manufacturing.

1-                 Flammable or combustible liquids shall be stored in tanks or closed containers.

2-                 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:

Ø            25 gallons of Class IA liquids in containers

Ø            120 gallons of Class IB, IC, II, or III liquids in containers

Ø            660 gallons of Class IB, IC, II, or III liquids in single portable tank.

3-                 Flammable liquids shall be kept in covered containers when not actually in use.

4-                 Where flammable or combustible liquids are used or handled, except in closed containers, means shall be provided to dispose promptly and safely of leakage or spills.

5-                 Transfer of flammable and combustible liquids must be provided with adequate ventilation.

6-                 Sources of ignition are not permitted in areas where flammable vapors may travel.

7-                 Emergency drainage systems shall be provided to direct flammable or combustible liquid leakage and fire protection water to a safe location.

·        Class I liquids shall not be dispensed into containers unless the nozzle and container are electrically interconnected.