A few years ago, when I wanted to learn just how toxic the inside of my home had become, I called on Albert Donnay, a Johns Hopkins–trained toxicologist. Donnay is a master at revealing the invisible and the dangerous. To do this, he walks around your house with his nose in the air. The first thing Donnay asks his clients to do is gather all of their cleaning products, laundry detergents, bug sprays, air fresheners, dryer sheets — in effect, anything they can smell — and dump it all in a big garbage bag. Then he has them tie the bag shut for a month. Once the month is up, he tells them to open the bag and … inhale. Donnay calls the garbage bag ‘the most effective thing I have to convince you to improve air quality in your home.