- Practice · 6 marks
Exhaust pollutants and emission norms
Short answer
Vehicle exhaust pollutants: CO from incomplete combustion reduces blood oxygen; HC unburnt fuel causes smog; NOx from high temperature causes acid rain; PM from diesel damages lungs. BS-VI (Euro6) limits sulfur to10 ppm. Compared to BS-IV, diesel NOx drops from0.25 to0.08 g/km, PM from0.025 to0.0045, requiring DPF and SCR.
Name the main pollutants from vehicle exhaust, their causes and their health effects. Briefly explain the emission norms (Euro, BS-VI and EPA) and the main differences between BS-IV and BS-VI.
Pollutants
| Pollutant | Cause | Effect |
|---|---|---|
| Carbon monoxide (CO) | Incomplete combustion in a rich mixture | Reduces the oxygen carried by blood; toxic |
| Hydrocarbons (HC) | Unburnt fuel, quench layer, evaporation | Smog; some are carcinogenic |
| Oxides of nitrogen (NOx) | High combustion temperature with excess oxygen | Acid rain, smog, lung irritation |
| Particulate matter (PM), smoke | Diesel: rich zones and fuel droplets | Lung and heart disease |
| Sulphur dioxide () | Sulphur in fuel | Acid rain |
| Carbon dioxide () | Complete combustion of fuel | Greenhouse gas |
Petrol engines mainly emit CO, HC and NOx; diesel engines mainly emit NOx and PM.
Emission norms
Norms are legal limits on the mass of pollutants per km (cars) or per kWh (heavy engines), measured over a standard test cycle.
- Euro norms (Europe): Euro 1 (1992) to Euro 6. The limits are tightened at each step; for example, for diesel cars NOx fell from 0.50 g/km (Euro 3) to 0.08 g/km (Euro 6).
- Bharat Stage (BS) norms (India): based on the Euro norms; BS-VI is equivalent to Euro 6 and was introduced in April 2020, skipping BS-V.
- EPA (USA): Tier 3 and California LEV standards, in g/mile, with a fleet average.
BS-IV vs BS-VI
- Sulphur in fuel falls from 50 ppm to 10 ppm.
- The petrol car NOx limit falls from 0.08 to 0.06 g/km; diesel NOx falls by about 70 % (0.25 to 0.08 g/km) and PM by about 80 % (0.025 to 0.0045 g/km).
- Diesels need a DPF and SCR, many GDI engines need a GPF, and on-board diagnostics (OBD-II) and real-driving-emission (RDE) tests are required.
✓ Answer checked by Claude Opus 5.5 (high effort)
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