The Bharat stage emissions standards(BSES) were set up and instituted by the Central pollution control board (CPCB) under the Ministry of Environment, Forest, and climate change. In the early days of its existence, the first emission norms were set for petrol engines in 1991 and diesel engines in 1992. As the Indian economy was in its millennium days of growth import and export were increasing so there occurs a need for international standards for emission controls to safeguard Indian products in the foreign market and to control pollution levels in India. It was in the year 2000 when India 200 emissions norms were enforced which were based on Euro 1 norms. Subsequently, BS 2 on Euro 2 in 2005, BS3 on Euro 3 in 2010, BS 4 on Euro 4 in 2017 as India has skipped the Euro 5 norms and introduced BS6 based on Euro 6 in the year 2020.

Source: Internet, Courtesy:

Need for the emission control norms & BS4 norms

As combustion of every fuel produces exhaust gas as it is a basic principle of chemistry. Diesel and gasoline also produce exhaust on combustion, the quantity of exhaust depends upon the speed of the engine (idling or speed under load). Diesel fuel’s exhaust consists of NOx, particulate matter, hydrocarbons. Gasoline fuel’s exhaust contains NOx, particulate matter in a less quantity than diesel. Diesel exhaust is placed in Group 1 carcinogen which causes lung cancer.

BS 4 norms were as follows

1. 2 wheelers: To reduce the evaporation emissions using carbon canisters, increasing the area and volume of catalyst to lower the emissions, automatic headlamp on to enhance the visibility of a two-wheeler on roads, and alert pedestrians of coming vehicle.

2. Petrol cars: ECU (electronically controlled unit) for fuel supply, ignition control, larger catalytic converter& OBD2.( onboard diagnosis which check the engine and other systems by giving warning lights on the dashboard like check engine light, ABS light, electrical fault, glow plug check light, brake system alert, etc.)         

3. Diesel cars and commercial vehicles: Diesel engines require to have a big catalytic converter, common rail fuel system, OBD2, Diesel oxidation catalyst(DOX), NOx sensor in the tailpipe. Big commercial vehicles require to have an exhaust gas recirculation(EGR)of about 60%.


In the wake of the Paris agreement of 2016, the need to reduce the sulfur content is considered seriously and India adopted BS6 norms which primarily focuses on reducing the sulfur content. The BS6 compliant fuel will be having very low sulfur content to 10 mg/kg. BS-IV fuels contain 50 parts per million (ppm) sulfur, the BS-VI g fuel has 10 ppm sulfur. BS 6can bring PM in diesel cars down by 80%. The BS6 norms will bring down nitrogen oxides from diesel cars by 70% and in gasoline cars by 25 %.

    sulfur has very good lubrication property on combustion so certain other additives are added to maintain the lubrication of the oil. Initially, BS6 compliant fuel will be slightly expensive due to less availability and addition of extra chemicals.


1. 2 WHEELERS: All two-wheelers are powered by petrol. Due to BS6 norms, two-wheelers have to be equipped with ECU & direct fuel injection technology with fuel injectors which means no carburetor. (carburetor: it is a component that uses high-pressure fuel and mixes it with high-pressure air and then feeds it to the cylinder for combustion. All types of petrol engines use carburetor technology to have a desired A/F ratio.). Due to this cost of vehicles has increased.

2. Petrol cars: OBD (Onboard Diagnostics), RDE (Real Driving Emission), end of carbureted type engine and use of gasoline direct injection (GDI), Direct injection, port injection technology to have more control over A/F ratios.

3. Diesel and heavy-duty commercial vehicles: The Selective Catalytic Reduction (SCR) unit converts nitrogen oxide (NOx) into diatomic nitrogen and water with the help of a catalyst. The SCR unit uses AdBlue to reduce NOx emissions. This fluid is made up of two compounds urea and deionized water. When exhaust gases come in contact with the AdBlue fluid, urea is converted to ammonia and carbon dioxide. The ammonia converts NOx into nitrogen and water vapor, thereby reducing pollutants. The AdBlue will be filled in a 10-liter capacity tank in smaller passenger vehicles. A full tank of AdBlue can go for 10000Km and be replaced during service intervals.

As per the supreme court judgment of 2020, no new vehicle can register for BS4 compliance. The second-hand car market will remain functioning for BS4 compliant vehicles. Also, the BS6 fuel will work perfectly fine in BS4 type vehicles.


The automobile sector in India has shown a remarkable presence and growth. India emerges as one of the potential auto markets for various automobile companies. But, as the number of vehicles increases many issues come to play. The most important issue is pollution from vehicles and the scrapping of older vehicles. India is looking forward to adopting a vehicle scrappage policy which is a win-win for all. From the market point of view, it is a market with a potential of $6 billion as the number of vehicles reduced will be 9 million by 2021 and 28 million by 2025. It will also help in clearing older BS1, BS2, BS3 type vehicles which will save 8 million tonnes of oil in a year. India is also focusing to lay down scrap plants near ports and increasing the depth of ports by 18 m so that big vessels can enter the port harbor and recycled parts can be exported. The recycled steel will save Forex of the nation, as India has to import steel to complete its need. There will be a proper disposal policy and norms for harmful components like plastic, rubber, AC systems, and electronic parts. Due to this policy, new and eco-friendly vehicles will be on roads. There is also a provision for giving compensation to owners who are opting for scrappage policy.

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Authored By:- Cdt. Hardik Vats, TMI

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