India, Oct. 25 -- The air around Delhi-NCR is already toxic, and soon, most of North India will be wrapped in its annual winter blanket of smoke. What frustrates me more than the haze itself is the misplaced faith people have in cheap air purifiers. Somehow, we've convinced ourselves that a single Rs. 7,000 unit sitting in one corner of a flat will protect an entire family from Delhi's smog. It won't. Just look outside- the air quality is beyond what any consumer-grade purifier can realistically handle.

Yes, HEPA-based purifiers do work, but only within their limits. If you truly want cleaner air indoors, you'd need one purifier per room, doors and windows sealed most of the time, and the machines running almost 24/7. Even then, you must...