All the above elements can be represented in the fire tetrahedron of
Fig. 13.1.
Previous point 3 is represented by the fuel leg of the tetrahedron,
whereas points 1, 2, and 5 are the heat leg. Point 4, that is, the presence
of the optimum flammable atmosphere, is the chemical reaction leg. The
risk of fire or explosion is eliminated if at least one of the above legs
is removed.
Additional risk offered by charged objects is the impulsive current
that can possibly flow through persons upon touch and discharging to
ground. This current is generally well below the threshold of danger,
but in some cases might be above the tingling sensation and, therefore,
cause sudden shock and induce accidental falls.