I trusted this air purifier in Delhi’s toxic winter: No regrets

The mid-range smart air purifier does not just look good on paper but ticks all the boxes that I had set for enduring some of Delhi’s worst months indoors. Here’s my review of the AC4221 unit after two months of usage.

Design and display

The Philips air purifier sports a clean, metallic black finish that blends easily into home and office environments without drawing too much attention to itself. That said, portability is not really part of the pitch. At 6.5 kilograms, this air purifier is not one that you can casually carry from room to room. While it can be moved when needed, it is clearly meant to stay put once you have decided where it belongs.

Real-time PM 2.5 display panel with colour ring below. (Image: Karan Mahadik/The Indian Express)

The real-time PM2.5 display panel is fully touch-based, with no physical buttons, which keeps the air purifier looking clean and modern. The numbers are large and easy to read, letting you check air quality at a glance. A colour ring around the top display serves as another visual cue of how clean or polluted the air indoors is based on the colour gradations.

Colour indicator set to ambient lighting. (Image: Karan Mahadik/The Indian Express)

While the lighting can be set to ambient colours, you also have the option to turn it off completely if it interferes with your sleep. Setting up the device can feel a bit fiddly, especially when it comes to inserting the filters in the correct orientation. I had to closely refer to the diagrams in the user manual to get it right.

Air flow and purification

Nice design aside, let’s get down to the brass tacks. The AC4221 model comes with not one, but two Nano Protect filters comprising a pre-filter, HEPA layer, and double activated carbon layer for gases, dirty smells, etc. One filter goes at the top, and the other one goes at the bottom.

The air purifier comes with two Nano Protect filters. (Image: Karan Mahadik/The Indian Express)

While most devices on the market now come with HEPA filters, the spec to keep in mind while buying an air purifier is the clean air delivery rate (CADR). The Philips AC4221 boasts of a 600 m3/h CADR, which is noticeably higher than the 400 m3/h CADR that you generally see among budget air purifiers. This is what makes it suitable for larger spaces such as my living room-cum-dining area. The company further claims that its Nano Protect filters capture 99.97 per cent of particles that are as small as 0.3 microns.

One rule that kept coming up during my research was placement. Air purifiers work best when they are not tucked away in corners, since they need unobstructed air flow to pull in polluted air and push out clean air efficiently. I have used other air purifiers that vent clean air from the top, making placement more easier. However, the Philips AC4221 takes a slightly different approach. While it features a 360-degree air intake, the clean air is released only from the mid-section of the unit. Because of this design, it might benefit from being slightly elevated or in a more open area to circulate clean air across the room faster and more efficiently.

App connectivity and maintenance

While researching and scanning multiple Amazon listings, I noticed that app-controlled models were priced consistently higher than non-connected units, despite having largely the same technical specs. At first, the idea felt unnecessary. Did I really need my air purifier to connect to an app? As it turns out, yes. The Philips air purifier makes a strong case for it, offering smooth and intuitive control through the Philips Air+ app available for Android and iOS devices.

The air purifier can be controlled through the Philips Air+ app. (Image: Karan Mahadik/The Indian Express)

Thankfully, the AC4221 model supports 5GHz WiFi and is relatively easy to pair. You can use the app to switch between five fan speeds with Turbo mode being the highest but also the most loud (51.5 dB) However, when it is in auto or sleep mode and the air is clean, it makes almost no noise.

Another useful in-app feature is filter status, which lets you decide when to clean the filters and when to replace them entirely. As per Philips, the filters are recommended to be changed after nine months. But the sad reality of Delhi-NCR pollution might suggest otherwise. Amid several social media users saying that air purifier filters were hard to come by online, I checked Amazon and found that replacement filters for the AC4221 are in availability.

The particle sensor at the back also needs to be cleaned regularly with a swab. (Image: Karan Mahadik/The Indian Express)

Cleaning both the air filters with a soft brush was simple enough thanks to their mesh design. Just don’t forget to reset the filter status in the app once you’re done.

Verdict

At Rs 27,995, the Philips AC4221 air purifier feels like a good investment for Delhi-NCR living. It combines a high CADR, reliable filtration, sensible app features, and aesthetic design with mid-range prices. If you live in a high-pollution city and want an air purifier that quietly does its job even on those murky, apocalyptic days, the Philips AC4221 makes a compelling case.