Biological Sciences

Flammable and Combustible

Classification of Flammable Liquids based on Flash point and Boiling Point:

Flammable liquids are ranked according to how easy it is to ignite the vapours (temperature dependent). Flammable liquids can be ignited by a spark at lower temperatures than combustible liquids but both classes can burn. Read more about the storage and handling of flammable materials (PDF, 136kb) from Alberta Workplace Health and Safety. 

Class
Flash Point (C)
Boiling Point (C)
Example:
Flammable:
I-A
< 23
< 38
ethyl ether
I-B
< 23
> 38
gasoline, toluene, ethanol (95%-70%)
I-C
23-38
-
ethanol (50% - 20%)
Combustible:
II
38-60
-
Varsol, fuel oil#1
IIIA
60-93
-
fuel oil #4
IIIB
> 93
-
glycerine

Notes: 
The flash point is the minimum temperature at which a liquid in a container gives off sufficient vapors to form an ignitable mixture with air at the surface of the liquid. The lower the flash point, the easier it is to form an ignitable mixture.

Properties of Flammable Liquids sorted by: 
Storage Limits for Flammable Liquids in Laboratories (1):

Maximum Volume (L) of liquids of Flammability Class:
Location:
I
II
I + II + III
Flammable Storage Cabinet (2)
250
500
500
Room with fire-rated walls/door (3)
10
60
250
Room w/out fire-rated walls/door (3)
5
10
10
Notes:

1. information from Laboratory Chemical Safety at the University of Alberta - User Guide (Feb2000); derived from the Alberta Fire Code (1997).

2. Do NOT place the flammable storage cabinet near a room exit.

3. fire-rated door are designed to contain the fire for at least 45 minutes; rating shown on plate attached to edge of door

4. Do NOT store flammable liquids in a refrigerator unless it is rated as "Explosion Proof" or "Explosion Safe". Vapours that accumulate in a regular fridge can be ignited by the thermostat switch.