Safe Handling of Flammable Chemicals

Safe Handling of Flammable Chemicals
Laboratory personnel should know the properties of individual chemicals with which they work.
The more familiar one becomes with a chemical, the more likely he/she is to handle the
chemical in a prudent manner. There are numerous safety resources available to all employees
who may have questions regarding a particular chemical. If developed appropriately, the
laboratory’s chemical hygiene plan should contain written standard operating procedures for
those chemicals that pose a fire risk in the laboratory. Material safety data sheets (MSDS) are
available through the OESO, as is consultation on safety practices for particular chemicals. The
following are several practices which should always be implemented when handling flammable
chemicals:
 Flammable chemicals should be stored in appropriate areas within the
laboratory and away from any potentially incompatible materials (see Section
2, pages 7‐9). Storage of flammable chemicals outside an approved flammable
storage cabinet should be kept to a minimum.
 Purchases of flammable chemicals should be kept to a minimum.
 All sources of ignition (i.e., Bunsen burners, hot plates, electrical equipment,
etc.) should be eliminated from areas in which flammable or combustible
chemicals are used.
 Use the chemical fume hood to capture vapors when appreciable quantities of
flammable substances are being used.
 Only those refrigerators and freezers approved for flammable storage should
be used for the storage of flammable materials.
 Keep containers of flammable chemicals closed at all times when not in use.
Section 3 Fire Safety
Chapter 3
Defining Flammable and Combustible Liquids
Defining Flammable and Combustible Liquids
Flammable Liquids
Any liquid having a flash point below 100°F and having a vapor pressure exceeding 2068.6 mm
Hg (40 psia) at 100°F.
Class IA — flash point below 73°F and B.P. at or below 100°F
Class IB — flash point below 73°F and B.P. above 100°F
Class IC — flash point at or above 73°F, but below 100°F
Combustible Liquids
Any liquid having a flash point at or above 100°F
Class II — flash point at or above 100°F, but below 140°F.
Class IIIA — flash point at or above 140°F, but below 200°F.
Class IIIB — flash point at or above 200°F.
National Fire Protection Association (NFPA) System for Classification of Hazards
The NFPA diamond is a symbol used to identify the hazards associated with a given chemical to
rescue workers. Frequently this symbol is found on the sides of buildings where chemicals are
stored and on chemical containers. Below are shown the various hazards symbolized by the
diamond and the numerical code which indicates the severity of the hazard. Class IA & IB
flammable liquids have an NFPA Fire Hazard rating of 4. Class IC flammable liquids are rated as
3. Combustible liquids are rated as 1, or 2.
HEALTH HAZARD
4 — Deadly
3 — Extreme Danger
2 — Hazardous
1 — Slightly Hazardous
FIRE HAZARD
Flash Points:
4 — Below 73° F
3 — Below 100° F
2 — Above 100 F°, Not Exceeding 200° F
1 — Above 200° F
0 — Will not burn
SPECIFIC HAZARD
Oxidizer OX
Acid ACID
Alkali ALK
Corrosive CORR
Use NO WATER
Radioactive
REACTIVITY
4 — May detonate
3 — Shock and heat may detonate
2 — Violent chemical change
1 — Unstable if heated
0 — Stable
Section 3 Fire Safety
Chapter 3
Defining Flammable and Combustible Liquids
NFPA Fire Hazard Ratings of Some Common Laboratory Chemicals
NFPA Rating Flash Point (°C) Boiling Point (°C) Ignition Temp. (°C)
Acetaldehyde 4 ‐37.8 21.1 175
Acetic Acid (glacial) 2 39 118 463
Acetone 3 ‐18 5607 465
Acetonitrile 3 6 82 524
Carbon disulfide 3 ‐30.0 46.1 90
Cyclohexane 3 ‐20.0 81.7 245
Diethylamine 3 ‐23 57 312
Diethyl ether 4 ‐45.0 35.0 160
Dimethyl sulfoxide 1 95 189 215
Ethyl alcohol 3 12.8 78.3 365
Heptane 3 ‐3.9 98.3 204
Hexane 3 ‐21.7 68.9 225
Hydrogen 4 ‐‐‐ ‐252 500
Isopropyl alcohol 3 11.7 82.8 3
Methyl alcohol 3 11.1 64.9 385
Methyl ethyl ketone 3 ‐6.1 80 515
Pentane 4 ‐40.0 36.1 260
Styrene 3 32.2 146.1 490
Tetrahydrofuran 3 ‐14 66 321
Toluene 3 4.4 110 480
p‐Xylene 3 27.2 138.3 530
Storage of Flammable and Combustible Liquids Outside of Flammable Storage Cabinets
The maximum quantity of Class I Flammable Liquids outside an approved storage cabinet shall
not exceed 2 gallons per 100 square feet of laboratory space.
The combined maximum quantity of Class I, II and III Flammable Liquids and Combustibles
outside an approved storage cabinet shall not exceed 5 gallons per 100 square feet of
laboratory space.
Section 3 Fire Safety
Chapter 3
Defining Flammable and Combustible Liquids
Chemical containers, not actively being used, should not be stored in the work area of chemical
fume hoods. Too much clutter can disrupt air‐flow patterns and potentially compromise worker
protection.
Storage of Flammable Liquids in Refrigerators and Freezers
Per enforcement directive from the City of Durham Fire Marshal, all laboratory refrigerators
and freezers must be labeled to indicate whether or not they are suitable for storing flammable
liquids.
Refrigerators and freezers utilized throughout the University, Hospital, and Medical Center
generally fall within the following three categories:
1. Those designed to store flammable liquids with all electrical equipment that meets Class I,
Division I requirements.
2. Those that have been modified by a licensed electrician to meet the Class I, Division I
requirements.
3. Those “residential‐types” that cannot be utilized to store flammable liquids, but are used to
store other chemicals or laboratory reagents.
Those refrigerators and freezers which fall into either category 1 or 2 will require a blue and
white label which states that the device is approved for flammable storage. Those which fall
into category 3 will require a red and white label be affixed which states that the appliance is
not approved for flammable storage.
To request aid in identifying the category in which an appliance falls, contact the OESO Fire
Safety Division at 684‐5609.