13. ANALYSES OF FLUE GASES
For approximate determinations of the composition of the flue gases, the Orsat apparatus, or some modification thereof, should be employed. If momentary samples are obtained the analyses should be made as frequently as possible, say, every 15 to 30 minutes, depending on the skill of the operator, noting at the time the sample is drawn the furnace and firing conditions. If the sample drawn is a continuous one, the intervals may be made longer.
14. SMOKE OBSERVATIONS[71]
In tests of bituminous coals requiring a determination of the amount of smoke produced, observations should be made regularly throughout the trial at intervals of [Pg 274] 5 minutes (or if necessary every minute), noting at the same time the furnace and firing conditions.