Abstract: Apparatus to reduce exhaust pollution of internal combustion engines (12) comprises a manifold (26) connected to the cells of the battery (23) of the electrical system associated with the engine (12), the manifold (26) receiving gas/vapor emitted from the battery cells. The manifold (26) is connected by a line (27) to the fuel/air inlet manifold (14) of the engine (12), preferably via the gas recirculation line (22) connecting the crankcase ventilation to the inlet (14). Water vapor taken from the engine radiator (31) can also be drawn into the line (27) through an accumulator (28). A second battery (34) can also be connected to the accumulator (28) to increase the gas/vapor drawn into the inlet (14).