Black or White Smoke is an Indicator of Improper Combustion

Black or white smoke emitted from the boiler chimney indicates inadequate combustion leading to excess fuel consumption. Check boiler parameters and settings.

The colour of the smoke emitted from the boiler chimney is a good first check on combustion.

Black smoke

White smoke

Grey smoke

What it indicates

Low air to fuel ratio, i.e. oxygen deficient combustion

High air to fuel ratio, i.e. oxygen rich system

Optimum air to fuel ratio for combustion

Status of combustion

Incomplete combustion

Complete combustion but the excess air carries away useful heat energy

Complete combustion with minimised losses

Leads to

Excess fuel consumption due to high unburnt losses

Excess fuel consumption due to high stack losses

Optimised fuel consumption

Complete combustion with minimised losses leads to optimised fuel consumption by the boiler. This in turn results in reduced fuel bills.

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