As already mentioned, smoke is a primary sign of incomplete combustion since it is basically composed of very small unburnt carbon particles, therefore it is important to determine the smoke (soot) content of the flue gas. Using madur portable flue gas analysers gives you the opportunity to perform a soot test and determine oil burner condition and operating efficiency and safety. However, smoke spot testing will not indicate the presence of CO. Since smoke and CO will almost certainly coexist, both tests are necessary.
A smoke test is important. This procedure is generally done when servicing fuel oil furnaces or setting up power burners. If the air/fuel mixture is not correct, you will see it in the flue gas as smoke or soot. Generally, equipment is adjusted for a trace or less of smoke (some manufactures will tell you to set their units up for a trace of smoke, then back it off). Smoke in the flue gas eventually will create a soot build up in the furnace, and that will cause a whole list of problems, including difficulties with draft, efficiency, and carbon monoxide. The use of the flue gas analyser will then allow this somewhat empirical formula to be improved and correctly implemented.
The terms soot test and smoke test are used in different wasy in different countries. What you can see and measure is the smoke in the flue gas, but this causes the soot layer to form on the inner sides of the burner. No soot without smoke could be the catch phrase!
EFFECT OF SOOT ON FUEL CONSUMPTION
| Smoke Scale Reading | Burner Performance |
| 1 | Excellent - Little, if any, sooting of furnace or boiler surfaces |
| 2 | Good - May be slight sooting with some types of furnace or boiler but little increase in flue gas temperature or consumption |
| 3 | Fair - Substantial sooting with some types of furnace or boiler and will require cleaning more than once a year on most types of furnace or boiler. |
| 4 | Poor - This is a borderline smoke reading, some units may soot only moderately, others may soot rapidly. |
| 5 | Very Poor - Heavy sooting in all cases - may require cleaning several times during the season. |
| 6 | Extremely Poor - Severe and rapid sooting may result in damage to stack control and reduce overfire draft to danger point. |