Explosion-proof hot water heater with unsealed fuel combustion chamber

An explosion-proof hot water heater comprising an inner casing having conduit means to admit water in a water chamber thereof and to remove it therefrom, an outer skin casing spaced from said inner casing with thermal insulation between said casings, said inner casing being supported over a gas-fired combustion chamber at a lower end thereof, said combustion chamber having a sealed bottom wall and a circumferential side wall, a fuel burner in said combustion chamber, combustion air intake ports in said circumferential side wall above said sealed bottom wall, a support base for supporting said sealed bottom wall elevated from a support surface, air intake openings about said outer skin casing spaced a predetermined distance above said sealed bottom wall, air passage means communicating said air intake openings with said combustion air intake ports of said combustion chamber, and a gas vapour sensor secured in relation to said support base below said sealed bottom wall and adapted to cause said burner to be shut off upon detection of explosive vapours, said combustion air intake openings being disposed spaced above said combustion air intake ports of said combustion chamber, said air passage means being comprised of circumferential air deflecting wall spaced inwardly of said outer skin casing adjacent said air intake openings for directing air aspired by said burner downwardly towards said sealed bottom wall and then through passage means disposed spaced adjacent said combustion air intake ports, said air deflecting wall having a curved top portion defining an outer circumferential outer edge dimensioned to abut against an inner surface of a bottom portion of said outer skin casing.