The Centre has allowed retro-fitment of CNG and LPG kits in petrol and diesel vehicles that are compliant with BS-VI emission norm.

As of now, such modifications are permissible only in vehicles that are compliant with BS-IV emission norm.

"This ministry... has notified retrofitment of CNG and LPG kit on BS (Bharat Stage)-VI  gasoline vehicles and replacement of diesel engines with CNG/LPG engines in case of BS-VI vehicles, less than 3.5 tonnes," the Ministry of Road Transport and Highways (MoRTH) said in a notification.

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The notification lays down the type approval requirements for retro-fitment. CNG is an environment-friendly fuel and will reduce the emission levels of carbon monoxide, hydrocarbon, particulate matter and smoke as compared to petrol and diesel engines, the ministry said, adding that the notification has been formulated in consultation with stakeholders.