Numerous conditions can arise in connection with the operation of a boiler that produces explosive conditions.
The most common causes of furnace explosion is as follows.
a) An interruption of the fuel or air supply or ignition energy to the burners, sufficient to result in momentary loss of flames, followed by restoration and delay re-ignition of an accumulation.
b) Fuel leakage in to an idle furnace and the ignition of the accumulation by a spare or other source of ignition.
c) Repeated unsuccessful attempts to light off without appropriate purging, resulting in the accumulation of an explosive mixture.
d) The accumulation of an explosive mixture of fuel and air as a result of flame is at one or more burners in the presence of other burners, operating normally or during lighting of additional burners.
e) The accumulation of an explosive mixture of fuel and air as a result of a complete furnace flame out and the ignition of the accumulation by a spark or other ignition source, such as could occur where attempting to light a burner(s).
f) Purging with an airflow that is too high, which stirs up combustibles smoldering in hoppers.