I learnt this off Darwin
Building regs state boilers have to be a certain distance from the floor as fumes from fuel and the like are heavy and stay closer to the floor so under normal circumstances they boiler should be high enough that it won't spark anything.
Combined with it all being enclosed (at least anything modern) you should be totally safe under NORMAL circumstances.
However if you go pouring petrol all over the floor or storing dozens of barrels in your garage with plastic seals that degrade when exposed to said petrol leaking fumes and fuel all over the shop ike one familly did then yes it will go BOOM next time the system kicks in