1) Flue gas color. One can observe the flue gas color of the biomass-fired boiler. If the black flue gas emerges from the boiler chimney, it means that the biomass fuel is not burned sufficiently to result in the low fuel utilization.

2) Ash and slag in the furnace. One can observe the ash and slag shape of the biomass-fired boiler. If they are lumpy, it means that the fuel in the furnace is not burned sufficiently to result in the waste.

3) Boiler body temperature. One can touch the temperature of the boiler outer wall for heat dissipation by hand. If the temperature is too high, it means that the boiler itself does not do well in heat preservation, which causes a large amount of heat lost. For this reason, more fuel needs to be consumed per unit time to ensure the normal supply of boiler steam or hot water. At the same time, if the flue gas pipe’s temperature is too high, it is also an indicator of excessive fuel consumption.