Flammable and Combustible Liquid Safety

---

Flammable liquids are among the most common hazardous chemicals found in a laboratory. The primary hazard associated with flammable liquids is their ability to readily ignite and burn. The National Fire Protection Association (NFPA) defines a flammable liquid as a liquid with a flash point that does not exceed 100°F (38°C). Combustible liquids have flash points at or above 100°F (39°C). 

 

Flammable and combustible liquids exhibit multiple health hazards besides the risk of fire. Example are listed in the table below. The manufacturer's safety data sheets (SDSs) must always be reviewed to identify the specific hazards of chemicals, recommend personal protective equipment (PPE), and identify the best practices for storage. 

 

Flammable Groups Exhibiting Similar Health Effects
Aliphatic hydrocarbons	Narcotic, but their systemic toxicity is relatively low
Aromatic hydrocarbons	Potent narcotic agents and overexposure to vapors can lead to loss of muscular coordination, collapse, and loss of consciousness
Alcohols	Vapors can be moderately narcotic
Ethers	Exhibit strong narcotic properties and can be moderately toxic
Esters	Vapors may result in irritation to the eyes, nose, and upper respiratory tract
Ketones	Systemic toxicity is generally low

 

Tracking

• When receiving flammable or combustible liquids from the manufacturer or distributor, record the chemical information in the OSU online chemical inventory.
• If the flammable liquid is a peroxide forming compound, the appropriate labeling guidelines and disposal time frames can be found here.

Storage

• The Globally Harmonized System (GHS) hazard pictogram for flammable liquids should be incorporated with other hazard pictograms at the entrance to areas that contain flammable materials.
• Flammable liquids that are not in active use should be stored inside fire resistant storage cabinets when available.
• Always segregate flammable and combustible liquids from other hazardous chemicals such as corrosives or oxidizers.
• Flammable liquid storage areas should be labeled with a font size that is no less than one inch in height.
• Laboratory entrances containing hazardous chemicals should display the NFPA diamond labeled with appropriate hazard class ratings.

• Flammable liquids that require refrigeration must be stored in certified explosion-proof refrigerators. Never store flammable chemicals in a standard household refrigerator. There are several ignition sources located inside a standard refrigerator that can cause fire or explosion.
• Minimize the amount of flammable liquids stored in the laboratory. Use the table below to determine the amount of flammable liquids that can be stored.

Maximum Quantity per 100 ft2
Class	Without Flammable Cabinet	With Flammable Cabinet
I	7.5 L (2 gal)	15 L (4 gal)
I, II, III	15 L (4 gal)	30 L (8 gal)

*NOTE: Values above are general and subject to change depending on laboratory construction and location. For additional information, contact EHS.

 

I - Flash point less than 38°C

II - Flash point between 39 and 60°C

III - Flash point greater than 68°C

 

• Metal drums used for storing and dispensing flammable chemicals must be properly grounded or bonded. Ground cables should be available and utilized in laboratories using metal storage containers for flammable liquid storage.
• Container size restrictions for storing flammable and combustible liquids are based on the container type and the flammability of the liquid, as shown in the table below. 

Container Size of Flammable and Combustible Liquids
Container	Flammable Liquids	Combustible Liquids
Glass	Class IA - 0.5 L (0.12 gal) Class IB - 1 L (0.25 gal) Class IC - 4 L (1 gal)	Class II - 4 L (1 gal) Class IIIA - 20 L (5 gal)
Metal & approved plastic	Class IA - 4 L (1 gal) Class IB - 20 L (5 gal)  Class IC - 20 (5 gal)	Class II - 20 (5 gal) Class IIIA - 20 (5 gal)
Safety cans	Class IA - 10 L (2.6 gal) Class IB - 20 (5 gal) Class IC - 20 (5 gal)	Class II - 20 (5 gal) Class IIIA - 20 (5 gal)

• Flammable liquids in quantities greater than four liters should be kept in certified metal safety cans, which should only be used as recommended by the manufacturer. Include the following safety practices:
  • Never disable the spring-loaded closure
  • Always keep the flame-arrestor screen in place and replace it if it becomes punctured or damaged
• Specific areas should be designated for waste containers. The area should be labeled with a font that is no less than one inch in height.

Usage and Handling

• Label all chemical containers with the identity of the contents and associated warning information.
• When utilizing flammable liquids in the laboratory, flame retardant lab coats should be worn.
• Flammable liquids must be handled in a fume hood, unless it is known that the permissible exposure limit (PEL) and lower explosion limit (LEL) will not be exceeded. The LEL is defined as the minimum concentration of a particular flammable or combustible vapor necessary to support combustion in air. Below this level, the mixture is too "lean" to burn. The Upper Explosive Limit (UEL) is the maximum concentration of a gas or vapor that will burn in air. Above this level, the mixture is too "rich" to burn. The range between the LEL and UEL is known as the flammable range for that gas or vapor. It is never safe to work in conditions that exceed the UEL. The table below lists the LEL and UEL conditions for several common flammable chemicals. 

LEL and UEL %
Vapor	LEL	UEL
Acetone	2.6	13.0
Heptane	1.1	6.7
Acetylene	2.5	100.0
Hexane	1.2	7.4
Acrylonitrile	3.0	17.0
Hydrogen	4.0	75.0
Ammonia	15.0	28.0
Methyl Ethyl Ketone	1.9	10
Tetrahydrofuran	2.0	12.0
Gasoline	1.2	7.1
Diethyl Ether	1.9	48.0
Benzene	1.3	7.9
Isobutane	1.8	8.4
Butane	1.8	8.4
Isopropanol	2.2	12.0
Methanol	6.7	36.0
Pentane	1.4	7.8
Toluene	1.2	7.1
Ethanol	3.3	19.0
Carbon Disulfide	1.0	50.0

• Before handling flammable liquids, consider all potential sources of ignition. Flammable vapors are generally heavier than air and tend to settle, traveling along lab benches and the floor. 
• The transfer of material to and from a container can result in an accumulation of static charge on the container. When transferring flammable liquids, this static charge could generate a spark, thereby igniting the liquid. To make these transfers more safe, flammable liquid dispensing and receiving containers should be bounded together before pouring. 
• Keep flammable and combustible liquids away from strong oxidizing agents, such as chromic acid, permanganates, chlorates, perchlorates, and peroxides.
• Large containers, such as drums, must also be grounded when used as dispensing or receiving vessels. All grounding and bonding connections must be on conductive surfaces.
• Never heat flammable liquids with an open flame. Use steam baths, water baths, oil baths, hot air baths, sand baths, or heating mantles.
• Use caution when handling miscible solvent/water mixtures. These mixtures can still be flammable depending on the partial pressures involved.
• Treat water contaminated with water-immiscible solvents carefully. Hydrocarbon sheens provide adequate surface area for volatilization and ignition.
• When volatile materials are present, use only non-sparking, explosion-proof electrical equipment like explosion-proof refrigerators.
• Laboratory desks and furniture should be constructed of fire-retardant materials.
• Avoid wearing clothing made of synthetic materials like polyester while handling highly flammable materials. In the event of a fire, synthetic materials will melt and stick to the skin.
• When transporting organic solvent bottles, use secondary containers to prevent breakage and contain spills in case a bottle is dropped or strikes a surface.
• Use only ventilated explosion-proof ovens for flammable or combustible liquids, or materials that contain residual flammable or combustible liquids. 
• A spill containment kit should be available in the event of an accidental release. Kits should include appropriate absorbent materials.

Waste Disposal

Almost all flammable and combustible liquid waste is considered hazardous. Flammable and combustible hazardous waste must be disposed of according to local, state, and federal regulations. OSU guidelines for disposal of flammable and combustible liquid waste are presented below.

• It is best practice to utilize approved waste disposal cans, see below.
• Do not use consumer goods containers to store waste aggregation for disposal
• If specialized waste cans are not utilized, it is best to return the material to the original container and clearly label it as waste.
• Rags or paper towels soiled with flammable or combustible liquids should be segregated from common garbage. These materials should be placed in a disposal can like the one pictured below and disposed of according to hazardous waste guidelines.
• Flammable and combustible liquid waste must be segregated according to these guidelines:
  • Type A - "CHO" waste are hydrocarbons and oxygenated hydrocarbons
  • Type B - "Nitrogenated Hydrocarbons" include hydrocarbons with nitrogen containing functional groups
  • Type C - "Halogenated Hydrocarbons" include hydrocarbons incorporated with halogens
  • (A+B=B), [(A&/or B) + C=C]
• A chemical removal request form is required before any chemical can be picked up by EHS. Each container must be sealed and labeled with a Hazardous Chemical Surplus Tag (Form HM95-2).