Final answer:
Excess air in the combustion process ensures complete combustion and reacts chemically with the fuel gas.
Explanation:
Excess air in the combustion process:
- Excess air is supplied to ensure complete combustion.
- Excess air does absorb heat but does not carry it off through the venting system.
- Excess air is supplied at a draft control device to reduce the temperature of the hot vent gases.
- Excess air does chemically react with the fuel gas.
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