At 12.30 am on Tuesday, CPCB's information confirmed an AQI of 272 at Siri Fort, whereas IQAir reported a studying of two,449 for a similar location. This distinction led to widespread confusion amongst customers checking air high quality ranges on-line.
Totally different scales, completely different outcomes
Specialists clarified that each units of readings have been right, however they have been based mostly on completely different strategies and scales.
“The Indian AQI, developed in 2015, is calculated utilizing six key parameters — PM2.5, PM10, ozone, nitrogen dioxide, sulphur dioxide, and carbon monoxide. The graded scale, from good to extreme+, ranges from 0 to 500,” stated M.P. George, former extra director on the Delhi Air pollution Management Committee (DPCC).
“Globally, completely different programs exist, some vary from 0–10 or 0–100. IQAir, for example, makes use of a US-based mannequin,” he added.
The US Environmental Safety Company (EPA)'s AQI, on which IQAir relies, additionally follows a 0–500 scale however permits values past 500. Within the US mannequin, something above 301 is assessed as hazardous. In distinction, India's system caps readings at 500 since well being dangers are already extreme at that degree, and better values supply restricted sensible insights.
Sensors versus analysers
Specialists additionally identified variations in how information is collected. IQAir's index is especially based mostly on sensor information, whereas CPCB makes use of analyser-based, reference-grade displays. These are thought-about extra correct and standardised.
“I'd belief CPCB's information, because the calibration and reference strategies are recognized. We don't know the precise algorithms IQAir makes use of,” Dr George stated.
Each present the identical actuality
Regardless of the numerical hole, specialists pressured that each readings pointed to the identical scenario, Delhi's air was extremely polluted. The town's air high quality remained within the “very poor” class throughout and after Diwali, exceeding protected limits below each Indian and worldwide requirements.
