The BS-I regulation in India only allowed a maximum carbon emission of 2.72 g/km and a respirable suspended particulate matter discharge of 0.14. Additionally, a cap of 0.97 g/km on Nitrogen Oxides+ Hydro Carbons release. Under BSI, carmakers had to re-tune secondary air intake systems, exhaust gas recirculation systems, carburettors and add a tri-metal layer to the system.