House plants have been having a moment lately. In fact, 71 percent of North American greenhouses saw an increase in plant sales in 2020. And if you’ve ever bought a house plant from a local plant nursery, the staff there has probably told you that house plants can even clean the air in your home.

Now, we love house plants. They’re one of the least expensive and easiest ways to incorporate biophilic design into your home or office space, and they add color, texture, and life. But we wanted to fact check the claim that they purify the air because it seems too good to be true.

Do houseplants clean the air?

Let's examine the evidence. The claim that house plants can clean the air in your home stems from a single 1989 NASA study. Scientists were researching ways to purify the air inside the space station. Researchers for this study put 12 different house plant species in sealed chambers, including peace lily, Chinese evergreen, Gerbera daisy, and ficus. Then they added three different volatile organic compounds (VOCS) to the sealed chambers. VOCs are chemicals that can be emitted as gases in the air. Many have the potential to negatively impact health, causing symptoms like eye irritation, nausea, or even worsening asthma. This NASA study used three VOCs: formaldehyde, benzene, and trichloroethylene. The researchers recorded how much of these gases were left in the chamber with the plant after 24 hours. Across all the trials, between 10 and 70 percent of the VOCs were removed.

So what’s the catch?

Sounds like house plants do a good job of cleaning the air, right? In the strictest sense, they do filter these VOCs out of the air to some degree. But the conditions of this study don’t align with the conditions of people’s homes. After all, your home isn’t a sealed chamber—every time you open a door or window, that brings new air into the house. Additionally, to recreate the study's density of house plants per meter, you’d need 10-1000 plants per square meter for the plants to significantly alter the air quality. For reference, for a 650 square foot (60 square meter) apartment, you’d need a minimum of 600 house plants for them to effectively remove volatile organic compounds from the air. That’s a lot of house plants.

Even this lavishly green living room would not have enough house plants for them to effectively clean the air. 

Other Benefits of House Plants

So no, your house plants are not going to clean the air, because you’d need way more of them than what is practical. But there are still other reasons to get a house plant or three.

• They reduce stress! Taking care of plants has been shown to make people feel more relaxed in several scientific studies, like this one.
• They add color and texture—whether you choose an all-green plant, or a plant with more colorful foliage, house plants enliven the look of your space.
• They’re generally inexpensive and easy to care for. (Unless you choose a fiddle-leaf fig. Don’t get us started on this notoriously finicky species.)
• They give you something to take care of if you can’t have pets at your place.
• They work in any décor scheme. You can choose dramatic striped plants like spider plants if your style leans modern or contemporary, or vined plants like pothos for a bohemian space. Or you can go for delicate-looking orchids or peace lilies if your home is Hollywood glam, art deco, or traditional.

So there you have it. House plants don’t clean the air in the way the NASA study might make you think. But they offer many other benefits. Have any other questions about house plants? Tell us in the comments below!