Air Fresheners Are Kind of Like Spraying Exhaust Fumes in Your House

We tend to think of air pollution almost exclusively as an outdoor phenomenon. Unfortunately, however, a new study shows that indoor products like flameless candles and wax melts can make the air quality inside even worse than it is outside, releasing extremely small particles that can get buried deep in your lungs and pose long-term respiratory health risks.

Scented wax melts look like chocolate bars that can be broken into individual pieces. You set these scented pieces over a flame or light bulb to melt the wax, releasing the scent into the air. It’s just melting wax, what can be so bad about that? A lot, it turns out.

When heated, the wax releases terpenes, which are aromatic compounds found in plants. When terpenes interact with indoor ozone, they form tiny particles smaller than 100 nanometers. They are produced in concentrations similar to those found in admissions from diesel engines and even gas stoves. These nanoparticles waft into the air, into your nose, and deep into your lungs. You may not realize it, but you’re breathing in a potentially harmful substance.

The research, conducted in Purdue University’s Zero Energy Design Guidance For Engineers Lab, was designed to test how everyday products and home activities affect indoor air quality. The researchers found that the nanoparticles released from scented wax melts could fill your lungs with up to 29 billion particles per minute, with a good chunk of those particles reaching your upper airways and even potentially entering your bloodstream.

While the health impact of terpenes is still not completely understood, they can be found in all kinds of pleasantly scented products, from wax melts to floor-cleaning solutions to aerosol sprays.

None of this is to say that you should immediately stop buying these products to protect your precious lungs from incurring immediate damage. However, the researchers do conclude that the designers of home HVAC systems should take the terpenes released by these home fragrance products into account when creating systems to filter out impurities in the air.

Sure, maybe that leads to a future where HVAC systems are so good they immediately remove the delicious scent you just put into the air, but if they protect your lungs maybe in the long run it’s not such a bad thing that your house smells like a pig stye.