What measures are taken to prevent harmful emissions into the atmosphere by heat engines?

Various measures are being taken to prevent harmful emissions into the atmosphere from heat engines. A special adjustment of the engines is carried out for a more complete combustion of fuel, which leads to a decrease in the content of carbon monoxide in the combustion products and an increase in the efficiency of the engines themselves. Designs of heat engines operating on a mixture of oxygen and hydrogen, as well as electric vehicles are being developed.