A hand pump draws a fixed volume of flue gas, usually ten strokes, through a strip of filter paper, and the spot is compared with a printed scale where 0 is clean and 9 is black. Oil burners are set for zero or a trace of smoke before final adjustments are made for O2 and CO2. A high smoke number means soot will build up on the heat exchanger and stack temperature will climb.
Smoke spot's a 3, open the air band a touch and pull another one before you go chasing the CO2.
Also heard as
- smoke spot test
- smoke test
- Bacharach test
Related terms
Nozzle
The precision tip on an oil burner that atomizes oil into a fine cone-shaped spray, rated in gallons per hour.
Sooted up
Coated with soot on the fire side, from rich or poor combustion, so heat transfer and draft suffer.
Combustion analysis
Testing a burner's flue gas for oxygen, CO, CO2 and temperature to set it up safely and efficiently.
Running rich
Burning with too much fuel for the air available, so combustion is incomplete.