Ravi Meattle is a stickler for hygiene, wellness and good living. This winter, the 73-year-old resident of Central Delhi has been taking great care to ensure his air purifier is working fine. Meattle gets the gadget's filters vacuum-cleaned every week so that they are able to absorb the dust and pollutants that he says would otherwise have settled on his lungs, He adds that with the kind of Air Quality Index (AQI) levels prevailing in Delhi, he discards the filter within six months and buys a new one, even if it sets him back by Rs 6,000- Rs 8,000. But