Abstract: The aim of this study was to determine carbon monoxide of exhaust gas emission in vehicles at Kalasin roads. The method detected carbon monoxide that used multi gas monitor AS8900 in different vehicles such as motorcycles, cars, tuktuk (motor tricycle), vans, trucks, buses and tractor at Kalasin roads. The results found carbon monoxide of exhaust gas emission in vehicles such as motorcycles, cars, tuktuk (motor tricycle), vans, trucks, buses and tractor were 137.67±17.24, 170.33±15.94, 640.00±118, 172.50±21.9, 208.00±0.54, 799.00±106 and 9.50±0.70 ppm, respectively. Percent of oxygen of exhaust gas emission in vehicles such as motorcycles, cars, tuktuk (motor tricycle), vans, trucks, buses and tractor were 19.00-21.00%. The highest carbon monoxide of exhaust gas emission was bus (799.00±106 ppm). Carbon monoxide (CO) is a product of incomplete combustion and happens whilst carbon inside the fuel is in part oxidized as opposed to fully oxidized to Carbon dioxide (CO). Carbon monoxide reduces the glide of oxygen inside the blood move and is especially, risky to individuals with heart sickness.