My dear grandma Cora always grew geraniums — red geraniums, to be specific. Nearly every time I went to went to visit her she had pots of them flowering outside the front door. I would gently stroke the leaves and breathe in that unmistakable geranium smell. To this day I love the smell of geraniums so much I grow them myself — all year ’round.

Now I’ve discovered that retaining the memory of that smell could help save lives. The same holds true for the smell of garlic, horseradish and other common odors. If suddenly detected in the wrong place at the wrong time, it could signal that a chemical weapons attack is underway.