• The Edict

Do Air Purifiers Work in Ashoka? Check out this Experiment

Fahad Hasin, UG20

*Kindly note the article should not be treated as a rigorous scientific experiment — simply because it was never meant to be, and hence not designed as such. I did this only for the sake of my personal curiosity. However, with the return of smog and the conversations around it, I thought it would be helpful to share the results with everyone on campus.

“Are air purifiers any good?” is something I have often overheard at Ashoka and wondered the same myself. My roommate and I recently got an air purifier and I was curious to know how effective it really is. I decided to compare the quality of air at various locations to test whether there is any significant difference (thanks to Sachin Bhatia (UG 20) for lending me his real-time PM 2.5 level monitor that enabled me to do so).

As per the PM 2.5 level monitor I was using, here are what different levels (in μg/m3) mean:

0–30: Good

30–50: Moderate

50–100: Poor

100–150: Unhealthy

Above 150: Very Unhealthy

I am not sure whether there was any category above the ‘very unhealthy’ as the maximum level of PM 2.5 I encountered that day was 205 μg/m3.

First, I took the readings in outdoor areas and compared it with some common indoor areas. The results suggested that there is a considerable difference in the PM 2.5 levels indoors and outdoors. Then, I compared two rooms in the same dorm on the same floor, adjacent to each other so that they are almost similar and, therefore, comparable. The air quality was relatively better inside both the rooms as compared to the corridor. However, it was still ‘poor’ inside the room without air purifier. The room with air purifier had a significantly better air quality. The results make a good case for the administration to invest in air purifiers, possibly by integrating HEPA filters with the existing air-conditioning system. Here are a few snapshots for your reference:

Outdoor areas

The readings were taken on 8th November 2019 between 7:00 and 7:15 PM


SH3 Common room: 144 μg/m3


SH3 courtyard: 158 μg/m3


Outside new academic block: 172 μg/m3


Outside Library: 172 μg/m3

Common indoor areas

The readings were taken on 8th November 2019 between 7:15 and 7:25 PM


AC-02–005: 111 μg/m3

AC-02–001: 77 μg/m3


Inside Library: 42 μg/m3

The air quality inside the library was surprisingly good (relatively). The readings were taken on 8th November, when there were no air purifiers in the library.


Inside room (without air purifier): 95 μg/m3

As expected, the above results show that there is a considerable difference in PM 2.5 levels indoors and outdoors. The next step was to test the effect of air purifier in the room.

Comparing rooms with and without Air Purifier

In order to test the effect of air purifiers, I needed two spaces that are almost the same except that one has an air purifier and the other does not. For this, I chose my room (925) and my friend’s room which is adjacent to my room (924). My room had an air purifier whereas the adjacent room did not. Hence, my room was effectively the ‘treatment’ and the other room was the ‘control’.

Control: Without air purifier (924 SH3)

Treatment: With air purifier (925 SH3)


PM 2.5 level in the corridor, right outside the room: 207 μg/m3 | Time: 8:20 PM

PM 2.5 level in room 924 (without air purifier) with AC turned off: 95 μg/m3


PM 2.5 level in room 925 (with air purifier) with AC turned off: 25 μg/m3


PM 2.5 level in 924 (without air purifier) with AC turned on: 72 μg/m3


PM 2.5 level in 925 (with air purifier) with AC turned on: 15 μg/m3


As it is clear from the PM 2.5 readings above, there was a significant difference in the PM 2.5 levels in the rooms with and without air purifier — the former having a significantly better air quality. It holds true both with and without the AC running. At an overall level, the PM 2.5 levels are much lower indoor areas as compared to outdoors. However, the levels are still poor/unhealthy even inside the rooms (without air purifiers). The room with an air purifier was the only area that had a safe PM 2.5 level. Note that the readings were taken on 8th November, when the air quality was supposedly ‘better’ or ‘normal’. However, as the readings show, it was only ‘less worse’ — it was still extremely unhealthy at an absolute level, as it is almost throughout the year. I am not sure about the efficacy of the air purifier in extreme conditions like smog days.


I believe that the extremely dangerous level of air pollution throughout the year makes a good case for the university to invest in measures for mitigating the effects of air pollution. As per Rithupar Pathy, the Deputy Campus Life Minister, the administration is planning to tackle the issue by having another water cannon and more indoor plants. However, in my opinion, that is far from enough given the level of pollution we have on ‘regular’ days throughout the year, let alone the smog days! The only effective solution I can think of is to have a centralised air purification system, possibly by integrating the existing air conditioning system with HEPA filters.

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