New Delhi, Nov. 11 -- Every winter, Delhi's pollution levels turn the air into a visible health hazard. With AQI numbers crossing into "severe" territory once again, people are staying indoors, but the toxic air is still finding its way into homes. Households are switching on air purifiers 24/7, hoping to keep respiratory illnesses at bay. Naturally, filter sales and purifier usage are at an all-time high.

But a growing number of users are asking the same question:

Do I really need to keep replacing these filters or can I just wash and reuse them?

In a city where the air purifier itself costs less than a year's worth of replacement filters for some models, the concern makes sense.

However, experts warn that the wrong cleaning method o...