What are BS-I, BS-II, BS-III, BS-IV, and BS-VI Emission Norms?

There is no denying that cars do radiate considerable levels of noxious gases. To curb car emissions, the Indian government announced its first Bharat Stage regulation in 1989. With the number of cars plying on the road increasing annually, BS-I wasn´t enough to keep pollution levels down. So the government began to upgrade accordingly. After BS-I regulation, the government rolled out BS-II, BS-III, BS-IV, with BS-VI, being the latest.

This article will walk you through all the different Bharat Stage regulations implemented over the years. Let's get started!

What is BS I?

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.

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What is BS II?

Under the Bharat Stage-II, the maximum permissible sulphur content in fuels was restricted to 500 PPM. In terms of emissions, acceptable Carbon Monoxide emissions were 2.2 g/km, respirable suspended particulate matter discharge was 0.08, and 0.05 g/km was the maximum discharge limit for Nitrogen Oxides and Hydro Carbons.

Instead of the carburettor, car makers had to equip the automobiles with a Multi-point Fuel injection system.

What is BS III?

In 2010, the government declared BS-III norms to be mandatory. As per BSIII, permissible levels of Respirable suspended particulate matter discharge is 0.05, Hydro Carbons+Nitrogen Oxide discharge is 0.35 g/km, and 2.3 g/km is the cap for Carbon Monoxide emission.

This new norm also restricted the sulphur content in fuels to 100 PPM. Also, installing a catalytic converter was a part of BSIII to handle Hydro Carbons and Carbon Monoxide.

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What is BS IV?

Sulphur content dropped by a whopping 50PPM in BS-IV norms. To ensure compliance with BS-IV, manufacturers equipped cars with bigger-sized catalytic converters. To ensure efficient combustion, they also tweaked the ECU. The new regulations also called for modifications in the exhaust and air intake systems.

The maximum Respirable suspended particulate matter discharge allowed was 0.025 and 0.18 g/km for Hydro Carbons+Nitrogen Oxide discharge.

What is BS-VI?

BS-VI is the latest emission norm in India. AS per BS-VI, the sulphur content in fuel has been slashed down by a whopping five times to 10 PPM. It also restricts tailpipe discharge from cars running on petrol.

For diesel models, the peak level of carbon monoxide should not exceed 0.50 g/kg. It also limits the Hydro Carbons+Nitrogen Oxide discharge to 0.15 g/km. As for petrol cars, the Respirable suspended particulate matter maximum discharge level is  0.05.

How Has The Rollout of BS-VI Affected BS-IV Cars?

With the announcement of BS-VI norms in India, the car models running on BS-IV or older fuels had to switch to cleaner fuels. You might already know that the BS-VI fuel's sulphur content is much lower than its predecessors. As a result, implementing BS-VI fuel has curbed harmful emissions from automobiles.

Coming to the effect of BS-VI on BS-IV cars, some did some minor tweaks eventually. Since sulphur acts as a lubricant for diesel engines, your vehicle might require routine maintenance to prevent wear and tear.

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Car owners must learn about the Bharat Stage emission standards. Hopefully, the updated emission regulations will give Indian automakers an environment-friendly approach.