Starting from November 1, vehicles lacking valid Pollution Under Control (PUC) certificates will be prohibited from entering Delhi. This measure is part of the revised Graded Response Action Plan (Grap) aimed at tackling air pollution in the National Capital Region (NCR). The Commission for Air Quality Management (CAQM) has mandated that fuel stations in the area deny service to vehicles without these certificates.

The Delhi Police has issued an advisory, emphasising strict enforcement of PUC norms. This includes impounding visibly polluting vehicles and imposing maximum penalties. Notably, even vehicles compliant with Bharat Stage VI (BS-VI) emission standards will require up-to-date PUC certificates to gain entry into the capital.

The PUC certificate serves as proof that a vehicle meets specific emission standards. It is obtained after a test that measures the emission of gases from petrol and diesel vehicles while the engine is idling.

Details of the PUC Test

The PUC certificate is mandated under Rule 115 of the Central Motor Vehicles Rules, 1989. It is required for all vehicles older than one year and is valid for six months, or twelve months for BS-IV and BS-VI compliant vehicles. Private testing centres authorised by state transport departments are responsible for issuing these certificates.

The test measures carbon monoxide (CO) and hydrocarbons (HC) emissions from petrol, CNG, and LPG vehicles. For diesel vehicles, a smoke test is performed to assess the darkness of exhaust smoke. The standards dictate that BS-IV vehicles must not exceed 0.3 per cent CO and 200 parts per million of hydrocarbons. Newer vehicles are also tested at higher engine speeds to ensure compliance.

However, research indicates that the PUC test may not accurately reflect real-world emissions, particularly for nitrogen oxides and fine particulate matter. A study by The Energy and Resources Institute (Teri) revealed that vehicles contribute to 81 per cent of nitrogen oxides in Delhi, which are precursors to harmful air pollutants.

Impact of Vehicle Emissions on Air Quality

The winter haze in Delhi is predominantly caused by particulate matter 2.5 (PM2.5), which poses significant health risks. A major study conducted by IIT Kanpur, IIT Delhi, and Teri analysed air quality from November 2022 to February 2023, finding that PM2.5 levels averaged 192 micrograms per cubic metre, exceeding the national standard of 60 micrograms.

According to the study, secondary inorganic particles formed from various sources contributed significantly to air pollution, with vehicles accounting for 17 per cent of PM2.5 emissions. The remaining sources included biomass burning and industrial activities. The research highlighted the need for comprehensive measures to address the multifaceted nature of air pollution in the region.

Furthermore, the PUC test has been critiqued for its inability to measure nitrogen oxides effectively. Idle tests do not replicate typical driving conditions, leading to underreporting of emissions. Studies have shown that faulty catalytic converters can significantly increase nitrogen oxide emissions, which the current testing methods fail to capture.

In light of these findings, the Delhi Assembly has requested a report from the transport department by January 31, 2027, on actions taken in response to recommendations from the Comptroller and Auditor General’s audit.

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