It is a purified world in Kerala, the land of trees. A big, spreading tree purifies as much air as a room air-conditioner. And the former is never switched off. The prolific, bustling, vegetation acts like a massive, biological, air-filtration plant working round the clock, round the year. Hence spending days in Kerala countryside is as if spending in an air- purified environs; some times better than it. So is the rejuvenating effect of the lush greenery of the state.