0729 Combustion air
0730 Three kinds of draft
0731 Natural draft burners
0732 Draft hoods
0733 Backdrafting
0734 Furnace room air openings
0735 Outside air supply
0736 Backdrafting
0737 Gas burners
0738 Monoport burners |  0739 Gas supply to burners
0740 Crossover igniters
0741 Refractory/fire pot
0742 Gas supply to burners
0743 Thermostat - bi-metallic (mercury bulb)
0744 Continuous pilot light
0745 Pilot light - relighting
0746 Scorching
0747 Heat shield or flame rollout shield |
