New Delhi, Jan. 7 -- It is easy to believe that a pet living in an apartment is protected from most dangers-no cars zooming past, no street dogs picking fights, and no monsoon puddles carrying infections. Yet the most serious risks to pets often sit quietly inside our homes.

Indoor air quality is a major culprit. We light incense during prayers, burn mosquito coils, and run diffusers because they smell pleasant. Dogs and cats breathe in the same particulate matter that irritates human airways, but they do it at the floor level where heavier particles settle. Cats groom themselves meticulously, so whatever lands on their coat ends up in their stomach. I have seen healthy pets develop chronic coughing or recurrent vomiting that improves si...