I was a repairman for a gas utility for a number of years, and investigated hundreds of complaints of carbon monoxide hazards.
The most people I ever packed off to a hospital from one call was eight. That was a restaurant where the manager had turned off the ventilator over the range to...
As a furnace repairman, my aim is to insure that equipment I repair does not exceed the BTU input rating specified by the manufacturer.
Clocking a gas meter often gives a reasonably good estimate of the BTU input if you get the BTU value of the gas per cubic foot from the gas utility.
But...
There are infra red flame sensors that only need to get a "look" at the flame, but I think you are referring to the flame sensors commonly in gas furnaces and equipment.
These types of flame sensor use a process of flame rectification to sense that the flame is lit, and they must be actually...