For millions across northern India, the November air tastes ashy, the sky looks visibly hazy and merely stepping outside feels like a challenge.

For many, their morning routine starts with checking how bad the air is. But what they see depends entirely on which monitor they use.

Government-backed apps like SAFAR and SAMEER top out at 500 - the upper limit of India's AQI (air quality index) scale, which converts complex data on various pollutants such as PM2.5, PM10, nitrogen dioxide, sulphur dioxide, carbon monoxide and ozone, into a single number.

But private and international trackers such as IQAir and open-source monitoring platform AQI routinely show far higher numbers, often shooting past 600 and even crossing 1,000 on some days.

This contradiction leaves people asking the same question every year: Which numbers should they trust? And why doesn't India officially report air quality beyond 500?

India's official air-quality scale shows readings above 200 pose clear breathing discomfort to most people on prolonged exposure. Readings above 400 and up to 500 are classified as 'severe' and affect healthy people while also seriously impacting those with existing diseases.

The scale, however, does not go beyond 500 - a cap set more than a decade ago when the National Air Quality Index was launched.

So why was that threshold introduced?

'It was assumed that the health impact would be the same no matter how much higher it goes because we had already hit the worst,' says Gufran Beig, founder director of SAFAR.

He admits that the 500 cap was originally set to avoid creating panic as crossing that mark signalled an alarming situation requiring immediate mitigation.

But this approach effectively flattens the data - anything above 500 is treated the same on official monitors, even if the real concentration is far higher.

'International organisations and portals don't impose such a cap,' says Beig. 'That's why we see numbers going much higher on global platforms.'

Experts also point out that globally, there's no universal AQI formula. Different countries apply their own pollutant thresholds, making it difficult to compare India's AQI to WHO or US standards directly.

With calls for a revision of India’s air quality framework, it’s clear that the current practices may no longer serve an increasingly dire environmental reality.