Delhi’s Air Pollution In Numbers

I spent a week in Delhi this winter, measuring the pollution levels inside the house, and outside. This is what I observed, and experienced.

“Numbers do not lie. Politics and poetry, promises, these are lies. Numbers are as close as we get to the handwriting of god.”Pacific Rim

I didn’t really care for the movie, but this line from “Pacific Rim” really left me thinking. Numbers are facts, they help us quantify the truth.

This winter, I didn’t want the pollution in Delhi to be a subjective topic. Pollution in Delhi has always been bad, but this time I wanted to put a number to it. So, I carried my PM 2.5 measuring device to quantify Delhi’s air pollution.

Measuring The Pollution In Delhi –  What’s The PM 2.5 Count?

We landed in the early hours of 24 December 2016 in Delhi, apparently one of the most polluted days since Diwali. We almost choked on the smell of diesel and smoke when we stepped out of the airport. It was no surprise that that night the PM 2.5 count was a shocking 558.

For the next 24 hours Delhi remained covered under a toxic cloud of pollution, and smog. During the day, the PM 2.5 count in South Delhi remained above the 450 mark. What was really shocking was the PM 2.5 count inside houses was above 300! Most houses in Delhi are not that well insulated from the outside, thereby allowing polluted air to easily come inside. There’s really no point “staying indoors”.

By Christmas evening the PM 2.5 count began to drop to below 300 as my air purifier struggled to clean the air indoors, and keep it clean.

It Gets Better, But Mornings & Evenings Worst

Over the next couple of days pollution levels began to drop off, relatively speaking. However, I started noticing a trend in Delhi’s air quality – mornings and evenings still remained the most polluted times of the day.

Throughout the during my stay, the PM 2.5 levels hovered between 250-300 during early mornings, and late evenings (and at night). A PM 2.5 reading that high translates to an Air Quality Index (AQI) of over 300, which is considered “Very Unhealthy” to “Hazardous”. So, it’s probably high time to rethink your morning or evening walks.

On the contrary the pollution levels would drop to about 150, the lowest, during noon. Still considered “Unhealthy” on the AQI, but the cleanest time (relatively speaking) of the day to step out of your house.

Everyday Should Have Been Red Alert

The cleanest day while I was in Delhi was on 1 January 2017, with the PM 2.5 count going to 96.3, that’s an AQI of 172 (see how to convert PM 2.5 readings to AQI). I never saw a reading lower than that.

So what did I learn? Even on the day with the lowest PM 2.5 count, Delhi should have hoisted a RED alert.

Recommended Reading  Delhi Is Choking Under A Toxic Cloud Of Dust And Pollution

How Effective Are Air Purifiers In Delhi’s Pollution?

With such toxic air quality, air purifiers, and masks are a necessity in Delhi. Air purifiers are probably the most effective in removing particulate matter from the air. However, as I observed this time, air purifiers can struggle to keep the air in your room or house clean. So, to ensure maximum effectiveness from your air purifier follow these steps :

  • Keep doors and windows shut at all times.
  • Keep the kitchen door closed while cooking.
  • Run the air purifier at maximum speed till the light indicates clean air. Almost all air purifiers have indications to show the quality of the air.
  • Keep the air purifier running throughout the day. I noticed that with Delhi’s toxic air quality, it takes less than a minute for air quality to deteriorate if the air purifier is turned off, or doors/windows are left open.

Best Air Purifier For Delhi’s Pollution

My criteria for air purifiers is simple – how much clean air does it deliver for the price. In that respect, I found that the Philips 1000 Series to fit the bill. It has a CADR (Clean Air Delivery Rate) of 270 m3/hour, which is sufficient for most rooms.  However, there are bigger and more powerful options available too on Amazon for bigger sized rooms.

The Budget Air Purifier

If price is your concern, then the simplest and most basic air purifier that you can buy for your money is a HEPA filter. Behind every great air purifier is a HEPA filter.

All you need is a HEPA filter attached to a fan. Check out my video below to see how effective a HEPA filter, attached to a fan, can be.

It may not be the most efficient, but it gets the job done.

Air Purifiers For Your Car

Yes, you can buy air purifiers for your car too. In fact, if you spend a ton of time driving on Delhi Roads, an air purifier for your car is a necessity. It’s probably more important, or as important, as an air purifier for your house.

I did manage to record the PM 2.5 while sitting in a car on Delhi roads. You can see the results below. Also, please avoid driving with the windows down.

Anti-Pollution Masks

I’ve used a couple of anti-pollution N99 masks, and the one that I highly recommend is the 3M 9332. These are disposable masks (so, do not reuse), and it’s best to buy a bunch of them, regularly.

Here is a link to other good respirators in case the 3M mask is out of stock.

Within a couple of hours’ usage in two days

Air Quality Monitor

And lastly, if you’re as concerned about air quality in Delhi as I am, buy a air quality monitor. They are slightly pricey, but will prove to be an essential tool to help you see the invisible.

Update, 6 January 2016

Since I published this blog, I’ve reached a lot of queries about air quality monitors from folks in India, and outside India. Although I’ve already mentioned the ones that can be bought on, I thought I’d add a few more that you can buy on

Air quality monitors for your home:

A slightly more pro air quality tester is the one from Holdpeak. It isn’t as pretty as the monitors mentioned above, but it would probably be really accurate to say the least.

The World Of Invisible Damage

We are limited by senses and, sadly, fail to react to a stimulant that falls outside the purview of our senses. Take the example of the sun’s invisible, yet harmful, UV rays.

One of my favourite photos is of Bill McElligott, a truck driver, who was exposed to the sun on the left side of his face for almost 3 decades. The constant and long term exposure to UV rays caused premature aging, and damage to a single side of his face. Bottom line – always wear sunscreen.

Similar to invisible UV rays, PM 2.5 particles are too small of our senses to pick up. Luckily we have sophisticated devices that can measure the amount of PM 2.5 in the air. Sadly, this information is not as widely reported or searched as say the weather forecast.

Pollution Is Too Blasé In Delhi

I was amazed at the reactions that I received for wearing an anti-pollution mask in Delhi. In fact, I was more shocked that no one else was wearing one!

I was told that “it’s always been this bad”. Without being completely objective, I guess it has been. Unfortunately, I too was indifferent before I knew the level of pollution in Delhi, and the harm it causes. But I now I always take precaution.

There’s a shocking lack of awareness, and inaction in Delhi (except for the man who stopped me in the middle of HKV to ask from where did I get my anti-pollution mask). I try my best each year to spread some awareness through this blog.

Recommended Reading  The World's Most Polluted City (By Far) - Delhi

Demonetization Or Pollution – Which Is Worse?

I honestly urge anyone reading this blog from Delhi to get rid of their “what can we do”, and “it’s like that only” attitude. Sure, everyone’s more than happy to debate and discuss the effects of demonetization. The only issue is – the damage done by demonetization will be reversed in a couple of years, but the damage done by air pollution will linger on for years to come.


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