English how-to · updated 2026
A daily city search in Delhi, Lahore, Beijing, and wildfire season in the US. This page has 50 important questions and answers. Original explainer for daily search — not a government login or live tracker.
AQI (Air Quality Index) turns pollutant measurements into a single colour-coded number so the public can see if outdoor air is a problem. Different countries use slightly different scales and breakpoints. In the US, EPA AQI runs 0–500 with bands from Good to Hazardous. India uses CPCB’s National AQI with similar colours but its own cut-offs.
The number is driven by pollutants such as PM2.5, PM10, ozone, NO2, SO2, and carbon monoxide — the worst pollutant that day often “leads” the index. A “Good” day is not a medical certificate, and a “Poor” day does not mean you must panic, but children, older adults, and people with asthma are usually told to ease outdoor exercise.
Check an official or well-known monitor (CPCB, AirNow, local EPA), not a screenshot from an unknown app. Indoor air can still be bad if you cook on solid fuel or smoke.
50 important questions. Quick 10 is a random set; Full set plays every question.
Original explainers for English readers — not copied match reports or official papers. Tap a question to see the answer.
Answer: Air Quality Index
It summarises outdoor pollution.
Answer: 0 to 500
Colours match the bands.
Answer: fine particles that can go deep into the lungs
It often drives winter AQI in many cities.
Answer: led by the worst pollutant that period
One pollutant can put the city in the red.
Answer: limit outdoor exertion, especially for sensitive groups
Follow local health alerts.
Answer: CPCB’s national AQI framework
Colours look familiar; numbers are not a copy-paste of EPA.
Answer: the same as weather (rain or heat) alone
You can have cool weather and bad air.
Answer: official or established monitors over unknown “AQI 999” stickers
Sensors need calibration.
Answer: coarser dust particles than PM2.5
Both can still irritate airways.
Answer: a pollutant in many summer AQI readings
It is not “fresh mountain air” automatically.
Answer: traffic and some combustion
Roadsides can read worse than parks.
Answer: some industrial and coal-burning sources
Local inventories differ.
Answer: a colourless gas that can also enter AQI when monitors include it
Indoor heaters have separate CO-alarm rules.
Answer: unusually sensitive people may notice effects
Read the local colour card.
Answer: children, older adults, and lung/heart disease
Others may still choose easier exercise.
Answer: about well-fitted respirators, not a loose fashion mask
Fit matters more than colour.
Answer: help if indoor sources are low
Cooking smoke indoors still counts.
Answer: cut some indoor particles if sized to the room
Filters clog; replace them.
Answer: PM2.5-led
AirNow-style maps are used in the US.
Answer: not always inside the same AQI number
Allergy forecasts are a second chart.
Answer: can be off by a wide band
Treat it as a hint.
Answer: spike particles for hours
Sensitive people stay in.
Answer: wash out some particles for a while
The next still day can rebound.
Answer: trap dirty air near the ground
Delhi-style smog stories use this word.
Answer: make the room worse than the street for an hour
Vent when outdoor air allows.
Answer: shorter, easier, or moved indoors
Follow the local health desk.
Answer: a local call when AQI is extreme
Check the day’s circular.
Answer: the US colour for little concern on that scale
India’s numbers are not a copy-paste.
Answer: look similar to other countries but breakpoints differ
Do not mix a US app with an India tweet blindly.
Answer: can disagree on the same afternoon
Look at which the app labels.
Answer: measure the air on your balcony
Use a live official monitor.
Answer: can cut some outdoor puff if filters are decent
Do not seal a running engine in a closed garage.
Answer: on sunny, still afternoons in some cities
The lead pollutant rotates.
Answer: PM10-ish near the site
Walk a street over if you can.
Answer: often a screenshot joke or a broken sensor
Official scales top out around 500 in many systems.
Answer: carry their usual inhaler plan on bad-air days
Follow their written action plan.
Answer: do not replace a purifier or a policy
Nice, not sufficient.
Answer: wide-area hints, not your street corner
Ground stations still matter.
Answer: a classic particle spike recipe
Plan indoor time.
Answer: weather, not a substitute AQI
Muggy and dirty can happen together.
Answer: not proof your lane is safe
Look at the nearest valid monitor.
Answer: closer to exhaust height on some pavements
Busy-road walks add dose.
Answer: cuts some indoor particles
Lid on the pan helps too.
Answer: a US-oriented official-style map many people use
India users lean on CPCB / SAMEER-type apps.
Answer: a reason to panic-buy oxygen cans as a first step
Follow health-department wording.
Answer: a public-health risk discussed in research, not a one-day quiz score
Policy and personal steps both exist.
Answer: a live AQI feed
Open CPCB or AirNow for today’s number.
Answer: adds a local puff the city index may miss
Switch off if you are waiting.
Answer: is weaker than a fitted respirator for particles
Better than nothing for dust; not magic.
Answer: outdoor ambient air in a monitoring method, not your blood test
Personal exposure still varies by street.
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