Final answer:
A common CO2 measurement for a gas-fired furnace is 8.5 to 9.5%. This measurement indicates the percentage of carbon dioxide in the flue gas emitted by the furnace and helps assess its combustion efficiency. Adjustments can be made if the CO2 measurement falls outside the recommended range.
Step-by-step explanation:
A common CO2 measurement for a gas-fired furnace is 8.5 to 9.5%. This measurement represents the percentage of carbon dioxide (CO2) in the flue gas emitted by the furnace.
By monitoring the CO2 levels, technicians can assess the combustion efficiency of the furnace. If the CO2 measurement falls outside the recommended range, adjustments can be made to optimize the furnace's performance.