Also, make sure the exhaust ventilation system is turned on
whenever the engine is running.
There are other substances in the shop that are harm-
ful if inhaled. One of these harmful substances is asbestos,
which may be found in the dust from a clutch disc or
older brake pads. Respirators (filter masks) should be
worn when working around any kind of airborne impuri-
ties, Figure 5-7. If welding during major engine repair or
in a machine shop, a special welding respirator should be
worn. It will trap toxic welding fumes and block them
from entering your nose, mouth, throat, and lungs.
Warning: A filter mask or respirator will
only protect you from the substances for
which it is rated. A dust mask will not pro-
tect against toxic fumes.
Chapter 5 Shop Safety 113
Fires Type Use
Class A Fires
Ordinary Combustibles
(Materials such as wood,
paper, textiles.)
Requires...
cooling-quenching
Class B Fires
Flammable Liquids
(Liquids such as grease,
gasoline, oils, and
paints.)
Requires...blanketing or
smothering.
Class C Fires
Electrical Equipment
(Motors, switches, and so
forth.)
Requires...
a nonconducting agent.
Class D Fires
Combustible Metals
(Flammable metals such
as magnesium and
lithium.)
Requires...blanketing or
smothering.
Soda-acid
Bicarbonate of
soda solution
and sulfuric
acid
Pressurized Water
Water under
pressure
Carbon Dioxide (CO2)
Carbon dioxide
(CO2) gas
under pressure
Foam
Solution of
aluminum
sulfate and
bicarbonate
of soda
Dry
Chemical
Dry Chemical
Granular type material
Not for use on
Okay for use on
Not okay for Not okay for
Okay for Okay for
Multi-purpose
type
Ordinary BC
type
Not for use on
Not for use on
Not for use on
Not for use on
Okay for use on
Okay for use on
Okay for use on
Okay for use on
Operation
Direct stream at base of
flame.
Direct stream at base of
flame.
Direct discharge as
close to fire as possible,
first at edge of flames
and gradually forward
and upward.
Direct stream into the
burning material or
liquid. Allow foam to
fall lightly on fire.
Direct stream at base of
flames. Use rapid left-
to-right motion toward
flames.
Smother flames by
scooping granular
material from bucket
onto burning metal.
Fire Extinguishers and Fire Classifications
A
B
C
D
A
A
A
A
A
B C D
B
B
B
B
C
C
C
C
D
D
D
D
A
D
B
C
A
D
B C
Old New
Old New
Old New
Figure 5-2. There are different types of fires. Fire extinguishers are rated by the type of fire on which they should be used.