Hazards of Chemicals and Gases
When some gases come in contact with certain other substances, spontaneous ignition may
occur. One of the better known of these reactions is that of oxygen with oil. Another reaction
is the possible ignition of hydrogen due to the heat of the reaction which liberated it, such as
sodium in water. Additional sources of ignition are as follows.
The spontaneous ignition that may occur in oily rags and other materials.
Smoking is a principal cause of fire, and calls for strict prohibition in hazardous
Other sources of ignition include sparks or flame-producing operations such as
grinding or welding, and equipment such as heaters or boilers.
Ferrous handtools can produce a spark when struck against, or by a suitable
object, and may cause ignition of some gas-air mixtures.
Other possible sources of ignition are internal combustion engines and battery-
powered electric vehicles.
The most disastrous accidents involving industrial gases have been caused by ignition of gas-air
mixtures. Fires cannot occur without three essential factors being present in the right quantity,
at one place, and at the same time. These factors are fuel, heat, and oxygen (which is normally
supplied by air). When they are present in the same place, in the right amounts, and at the same
time, there will be a fire. To prevent a fire, it is necessary to keep only one of these factors away
from the other two. Air is necessary for life and cannot normally be eliminated, but the fuel and
heat can be kept separated. Proper operational and maintenance procedures will help prevent
a flammable gas from escaping into the air, but because this is always a possibility, it is most
important to eliminate the source of ignition.
The important information in this chapter is summarized below.
Compressed Gases Summary
The following terms are defined:
Compressed gas is defined as any material or mixture having in the container an
absolute pressure exceeding 40 psi (pounds per square inch) at 70 F, or
regardless of the pressure at 70 F, having an absolute pressure exceeding 140 psi
at 130 F; or any flammable material having a vapor pressure exceeding 40 psi at