I’m sure you’ve heard of the Air Quality Index (AQI), but most people just hear the phrase and don’t know what it means. The Air Quality Index is thoroughly explained in this article, along with its applications and measurement methods. Now let’s study the Air Quality Index.
Stage I: Poor Air Quality (AQI 201–300)
This is the entry-level stage, activated to prevent worsening. Focus is on preventive and regulatory actions.
Key measures/restrictions (in addition to general citizen advisories):
Strict enforcement of dust control at construction sites (covering material, water sprinkling).
Ban on open waste burning, garbage dumping, and stubble burning in NCR.
Intensified checks on industrial emissions and PUC (Pollution Under Control) certificates for vehicles.
Promotion of public transport, carpooling, and the use of cleaner fuels/electric vehicles.
Restrictions on the use of diesel generator sets (DG sets) without adequate emission controls.
Enhanced road sweeping, water sprinkling on roads, and anti-smog gun usage.
Citizen charter: Maintain vehicle tuning, avoid idling, and use apps to report pollution.
Stage II: Very Poor Air Quality (AQI 301–400)
Builds on Stage I with more targeted curbs, especially on vehicular and commercial sources.
Key measures/restrictions (adds to Stage I):
Ban on entry of diesel medium goods vehicles (non-essential) into Delhi.
Restrictions on non-essential diesel four-wheelers (e.g., BS-IV diesel in some cases).
Increased parking fees in urban areas to discourage private vehicle use.
Ban on coal-based industries or units without emission controls.
Stricter dust mitigation at large construction projects; partial curbs on non-essential construction.
Enhanced enforcement against polluting vehicles and industries.
State governments may stagger office timings for the public sector.
Stage III: Severe Air Quality (AQI 401–450)
This stage (often called GRAP-3) involves significant restrictions to halt rapid deterioration, as seen in recent invocations (e.g., January 16, 2026, when AQI was around 368+ and trending up).
Key measures/restrictions (adds to lower stages; many are now more aggressive post-2025 revisions):
Complete ban on non-essential construction and demolition (C&D) activities (earthwork, demolition, piling, concrete mixing, plastering, painting, etc.).
Exemptions for essential/infrastructure projects (metro, rail, hospitals, defense, sanitation).
Vehicular curbs: Ban on BS-III petrol and BS-IV diesel four-wheelers in Delhi; restrictions on non-essential diesel medium/heavy goods vehicles; inter-state buses not meeting BS-VI/CNG/electric norms barred (exemptions for emergency, public transport, essential services).
Ban on use of coal/wood in restaurants/open eateries; closure of certain polluting units.
50% work-from-home or staggered timings for government/private offices (in some implementations).
Enhanced school closures or restrictions on outdoor activities for children.
Strict ban on firecrackers, waste burning, and DG sets without controls.
Intensified mechanical sweeping, water sprinkling, and anti-smog measures.
Stage IV: Severe+ Air Quality (AQI >450)
The most stringent emergency stage, invoked only when pollution is extremely critical (e.g., briefly in December 2025, revoked after improvement).
Key measures/restrictions (adds to Stage III; highly disruptive):
Severe vehicular restrictions: Potential odd-even scheme for private vehicles; near-total ban on non-essential private vehicles (only emergency vehicles allowed in extreme cases).
Mandatory work-from-home (up to 50–100%) for non-essential offices; possible closure of educational institutions.
Shutdown of highly polluting industries or non-compliant units.
Ban on entry of most trucks/goods vehicles (even stricter than Stage II/III).
Additional emergency steps like closure of non-essential commercial activities.
All lower-stage measures continue with maximum enforcement.
How AQI is Implemented
Stages are implemented/removed based on real-time AQI trends and forecasts (not just when a threshold is crossed once).
Measures under lower stages remain in effect even when higher stages are active or after they have been removed (e.g., after Stage IV was removed in December 2025, Stages I–III continued).
Exemptions for Essential Services
Exemptions often apply to essential services (ambulances, fire engines, police, public utilities, CNG/electric vehicles, etc.).
Adherence to GRAP Citizen Charter
Citizens are urged to follow the GRAP Citizen Charter at all stages: use public transport, avoid single-occupancy vehicles, report violations through apps (SAMEER, Green Delhi, 311), and minimize exposure to pollution. For the latest official details, refer to the CAQM website (caqm.nic.in), where the current GRAP schedule (revised in November 2025) and recent orders are published.
This plan is subject to change based on Supreme Court directives and seasonal patterns, and stricter actions will be triggered earlier in 2025-2026 to improve overall compliance.