Both the composition and harmfulness of exhaust gases emitted by the two-stroke engine of new Husqvarna and Stihl chain saws have been discussed in the paper. The research carried out on six chain saws (three chain saws from each of the manufacturers), with a different engine capacity, at several stages of work.. Moreover, possibilities of reduction and limitation of fumes emission are presented. As a result of the analysis of the research it has been stated that: the swept capacity of the two-stroke engine of a chain saw does not influence the size of the produced exhaust gases, and differences between the models and firms are not large. The work of a chain saw in the idle running causes a considerably higher emission of hydrocarbons (HC) than at other stages of work. And thus its work in low gear should be limited to the indispensable minimum; an increase of oxygen (O₂) quantity in the air-fuel mixture lowers the quantity of emitted carbon monoxide (CO). This phenomenon is connected with the suitable regulation of the chain saw carburettor.

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