Acetylene is a colorless and tasteless gas, possessed of a peculiar and
penetrating odor. The least trace in the air of a room is easily noticed,
and if this odor is detected about an apparatus in operation, it is certain
to indicate a leakage of gas through faulty piping, open valves, broken
hose or otherwise. This leakage must be prevented before proceeding with
the work to be done.

All gases which burn in air will, when mixed with air previous to ignition,
produce more or less violent explosions, if fired. To this rule acetylene
is no exception. One measure of acetylene and twelve and one-half of air
are required for complete combustion; this is therefore the proportion for
the most perfect explosion. This is not the only possible mixture that will
explode, for all proportions from three to thirty per cent of acetylene in
air will explode with more or less force if ignited.

The igniting point of acetylene is lower than that of coal gas, being about
900 degrees Fahrenheit as against eleven hundred degrees for coal gas. The
gas issuing from a torch will ignite if allowed to play on the tip of a
lighted cigar.

It is still further true that acetylene, at some pressures, greater than
normal, has under most favorable conditions for the effect, been found to
explode; yet it may be stated with perfect confidence that under no
circumstances has anyone ever secured an explosion in it when subjected to
pressures not exceeding fifteen pounds to the square inch.

Although not exploded by the application of high heat, acetylene is injured
by such treatment. It is partly converted, by high heat, into other
compounds, thus lessening the actual quantity of the gas, wasting it and
polluting the rest by the introduction of substances which do not belong