In this installment of Ingredients, chemist George Zaidan digs into a key ingredient of many citrus-scented air fresheners: Limonene. In addition to being a killer band name, Limonene is found in citrus peels, and it happens to react with ozone to create formaldehyde.

Before we go nuts on this formaldehyde thing, it's important to be clear that the amount of formaldehyde is low, and likely not an issue unless you're going vastly overboard with ozone generators (like some "air cleaners") and a lot of citrus-scented products. But it's fascinating to explore how the chemical interplay between two otherwise innocuous consumer products—citrus-scented air fresheners and ozone-producing "air cleaners"—can create a really nasty substance.

For five minutes of useful chemistry advice, tune in:

For more on the issues Zaidan mentions with ozone-producing air cleaners, check the various links in the YouTube video description. If you're more of a direct-link person, check out this explainer from the California E.P.A. or this PDF fact sheet from the Connecticut Department of Public Health.