Delhi air turns toxic again: 5 things to know about car air purifiers

It is that time of the year again in Delhi when a whiff of air can be absolutely lethal and residents gasp for breath each time they step out. With the AQI (air quality index) slipping to above 300 on Tuesday, the alarm bells have started ringing loud. And this may not even be the worst as crackers during Diwali and change in wind direction which could bring in polluted air from areas witnessing stubble burning could further deteriorate the toxic air cocktail.

It is because of Delhi's infamous track record with pollution in recent times that many OEMs have started offering air purification systems in their vehicles. Initially seen as a luxury only in high-end vehicles, even mass-market vehicle manufacturers are now offering air purifiers in upper variants of most of their models. These may be in-built or courtesy an external device placed in the cabin and powered through USB or 12V charging points. Then there is the option of purchasing such a device from third-party vendors as well.

But do air purification systems meant for cars actually work and can these promise to keep you safe at all times? Here are five things to note:

• There are multiple kinds of air purification systems meant for cars. Some claim to have activated carbon filter, others have HEPA and still others have both among other features. On paper, these surely work but in real world conditions, much would depend on a wide variety of factors.
• Having an air purifier in the car is absolutely meaningless if even one of the windows is open in a polluted environment. Many also claim that the air inlet system inside a vehicle must be put to re-circulation so that the polluted ‘fresh’ air isn't brought in. Such factors can make even the best of air purifiers work double hard to clean the cabin, thereby negatively affecting its performance and longevity.
• Many devices come with an AQI measuring feature and the figure is on display at all times. While obvious, the figures would always shoot up in case someone opts to light up inside the vehicle.
• It is also obvious that car air purification systems are not a complete solution each time someone steps out. While it is a good investment if someone spends hours inside a car each day, the cost of purchase and of getting filters replaced may be cumbersome even if there is really no price tag that ought to be put on breathing clean. A US Environmental Protection Agency (EPA) advisory states that filters in car air purifiers should be changed between three and six months. In Delhi, it is safe to assume that this time frame may well be a month at best considering the level of air toxicity here during winters.
• If out in the market for a car air purifier, check that its Clean Air Delivery Rate or CADR is more than 25 m3/ hour. For smaller vehicles, this figure is effective but for larger vehicles like SUVs, the higher this figure, the better.