Hazards of Chemicals and Gases
Oxygen (O ) supports combustion, but does not burn. Even so, it must be considered a
potentially hazardous element from a fire hazard standpoint. The results of an enriched oxygen
atmosphere include a lowered ignition temperature, an increased flammable range, and an
acceleration of the burning rate. Oxygen readily combines with other elements and compounds,
with spontaneous ignition in some cases. When oxygen comes in contact with oil, grease, or fuel
oils, it may ignite violently. Every possible precaution must be taken to prevent this
Oxygen sustains life, but if pure oxygen were inhaled continuously for extended periods, the
reactions in the body would be too rapid and would cause harmful effects. Oxygen should
always be referred to as oxygen, and not air, to prevent confusion. It should never be used to
run pneumatic equipment because of the possibility of coming in contact with oil that may be
inside the equipment. Finally, oxygen valves should be operated slowly. Abruptly starting and
stopping oxygen flow may ignite contaminants in the system.
Sources of Ignition
All known sources of ignition must be eliminated in areas that contain, or may contain,
flammable gases. This includes areas where gases are being manufactured or used in some
process and in areas where they are stored.
One potential source of ignition is electrical equipment. When used or installed in hazardous
locations, this equipment must be explosion-proof and properly installed.
Electrical equipment includes not only the more obvious equipment such as motors, generators,
motor controls, switches, and lighting fixtures, but also the not so obvious equipment such as
alarm systems, remote controls, telephones and other communication systems.
The use of unapproved portable electric tools and equipment should be strictly prohibited in
hazardous locations. When temporary lighting is used, it must be an approved type and in
All possible sources of static electricity should be anticipated to prevent its buildup and
discharge. Several methods of control may be used. It is necessary that conductive parts of a
system be bonded (described in the following chapter) together to eliminate the difference in
potential between the parts, and the whole system grounded to eliminate the difference in
potential between the system and ground.