The Bharat Stage (BS) is an emission standard developed in India, modelled on European standards, to regulate the amount of air pollutants emitted by vehicles. Vahan portal, the RC, Form 22 and the windscreen sticker can each reveal your vehicle's emission standard. Here is how to use them, and which to. To curb rising winter air pollution during the winter, the Delhi government is implementing a Winter Action Plan from November 1.