Air is most important for the public health point of view, because every individual person approximately 22000 times breathes per day and inhale 15 to 22 Kg of air daily. Air pollution can be defined as accumulation of materials in to atmosphere, which will have a dexterous effect on life upon our planet. Due to high cost and less output power of petrol engines, diesel engines are more in use rather than petrol engines but the toxic gases emitted in diesel engines are greater than petrol engines. The main pollutants contribute by automobiles are carbon monoxide (CO), unburned hydrocarbon (UBHC), oxides of nitrogen (Nox) and lead. Electric power generating stations, industrial and domestic fuel consumption also some other sources to air pollution. In this regard reducing toxic particle silencer (RTP) is introduced in the automobiles to control the noise and emissions. It is fitted to the exhaust pipe of engine. RTP silencer controls emissions by reducing the toxic particles in automobiles exhausts and it doesn’t require catalytic converter. In this paper, toxic content in petrol engine exhausts at various running speeds are studied by changing the lime stone content in RTP silencer. Reduction of HC and CO emissions are observed by changing the lime stone content from 25 to 150 grams.