Hey fine folks of r/india, this post is my own experiment of building a cheaper DIY air purifier as like most of you, I too live in a highly polluted city. Although one can buy an air-purifier directly, I feel the basic version would cost about 40-50%, and should be sufficient for most of our needs.

The presented version here is without any fancy electronics, anyone with basic craft can build it and costs around INR 4500 assuming one buys all the spare parts new from the links.

Disclaimer before I begin: I am not an expert in air-purifiers or any of the technology used for it. The stuff I’ve built is fairly simple with parts which you can either buy online or salvage it from an old hardware. I’ll be posting links to where you can avail the spare parts, but again, I don’t endorse anyone to buy it from there, I’m not affiliated with any company or any product. My only intention is to make use of my relatively expensive engineering degree, and inadvertently help someone. Lastly, one only needs to have the knowledge of how to buy things online, and assemble it with some duct-tape, glue and scissors.

This post will cover:

  • How to build a basic air purifier using HEPA filter which will be able to clean your air in your room of PM2.5 and PM10. PM 2.5 & PM10 are the particulate matter suspended in the air which cause the most damage to our lungs. (ref: Inhalable Particulate Matter & Health)

  • I’ll give you the empirical measurements from my setup, so one can estimate the time they have to keep their air-purifier ON for their own room.

  • Closing thoughts

Let’s get started:

Step 1: Sourcing the items for a basic air-purifier:

  1. 1X HEPA filter:As the name suggests, this is the filter which most of the air purifiers use. I would recommend getting Mi HEPA filter because of its shape and performance. I’ve used it for my purifier and it works well for me.

  2. 1X 12 V High speed BLDC Fan:This is the fan which will suck the air from your room and pass it through the HEPA filter thereby cleaning the air of PM2.5. Now here’s the thing, the more powerful fan you get, the faster your room will be cleaned, but also it will cost you more. I would recommend getting a bldc fan like this. I couldn’t find any links on amazon, but this fan is similar in power. I personally use an old server fan which I salvaged from an old server rack, it looks like this.

  3. 1X 220V AC to 12V DC converter:This is required to power the fan (as the fan runs on 12V). You can get a relatively inexpensive but powerful converter here. Alternatively, for all the tech-geeks out there, you can check your SMPS from your spare/old CPU, and if the ratings match, you can use it as well, save some bucks.

  4. Wire: Preferably high amperage electrical wire to connect fan and adapter.

Step 2: Assembly:

  1. Air purifier Body:

Open the HEPA filter from the box, but dont throw the box yet, we will use that our structure for our air-purifier body, like this:

r/india - [Show India] DIY Cheaper Air Purifier

Unpack the HEPA Filter. Remove the plastic packaging, but dont throw the box yet.

r/india - [Show India] DIY Cheaper Air Purifier

Make an opening at the top which we will use to fit the fan and the wire later

r/india - [Show India] DIY Cheaper Air Purifier

Make 4 more openings on the face of the box with of arbitrary size. Ensure the openings are not too wide to compromise the sturdiness of the box.

2. Mounting the fan

r/india - [Show India] DIY Cheaper Air Purifier

12 V BLDC Fan

r/india - [Show India] DIY Cheaper Air Purifier

We can’t see it, but trust me it happens.

3. Connecting the fan to powersupply

r/india - [Show India] DIY Cheaper Air Purifier

Quite simple honestly, connect the positive terminal to positive, and negative terminal to negative terminal on the connector. Unlikely you’ll get a shock, but be careful anyway.

4. Switch on the powersupply and it should start working, depending on power of the fan it maybe be bit noisy.

Yep, its bit noisy.


Typically Air purifier performance is measured in CADR, But I neither had equipment nor enthusiasm to do that. This is a small experiment I ran in a closed room ((15X15 ft) with air conditioning ON & OFF, and a PM2.5 measurement device (you can buy it or build it yourself using using an arduino and SDS011 sensor.

r/india - [Show India] DIY Cheaper Air Purifier

Within an hour there was significant reduction in the PM2.5 levels.

Closing Thoughts

  1. My consecutive experiments with Air Purifier reveal that in an hour it usually brings down the AQI to significantly lower numbers. But again, I’m not in Delhi, so I don’t know how well it will perform in polluted conditions.

  2. Instead of keeping it on throughout the day, I prefer keeping it ON for an hour per day in my closed room, typically in the evening, go out for a walk as its noisy, and then come back.

  3. The AC filters are definitely less clogged when I use air purifier. It should be having a positive effect on my lungs as well.

  4. For tech savvy people, we can further use DC-DC relays, integrate it with ESP8266 and make it as an iOT device.

Again there are so many things we can build on top of this, but this basic purifier should help a little in these polluted times in our cities. Hope it helps!