Can Indoor Plants Reduce Indoor Air Pollution?

Do plants improve your air quality? If you asked a group of people, they would probably say yes...

But what if you asked a group of academic researchers?

Today, we want to tackle the myths surrounding plants and air quality. Indoor air pollution has been gaining importance in the past years, especially since the Covid-19 pandemic had long periods of quarantine and indoor activities.

According to the Environmental Protection Agency (EPA), Americans spend up to 90% of their time indoors, where pollution levels can be up to five times higher than outside air.

But first, why does that happen?

What Makes the Indoor Air Polluted?

Some activities like cooking, lighting candles or incense, and smoking can generate pollution. Cleaning products commonly used in the house can also contribute to higher levels of toxic compounds in the air.

Know more about the difference between indoor and outdoor air in our recent blog.

Do Indoor Plants Help to Purify the Air?

A quick search on the internet will reveal many different opinions and studies pointing in opposite directions. While controversial, it is good to be informed and read from trusted sources. Here you will find a summary of some studies and their opinion.

Many wellness blogs and web pages contain information that plants help purify indoor air. They refer to a study conducted by NASA in 1989. The study set the plants in chambers just over two feet wide and long, filled with various gases circulating by a small fan.

It claimed that during the photosynthesis process, plants could inhale air pollutants and release clean oxygen into the room. However, multiple critics argue that the plants’ circumstances did not mimic the typical household or office environment.

Potted Plants Do Improve Indoor Air Quality

New research (March 7, 2022) led by the University of Birmingham and in partnership with the Royal Horticultural Society (RHS) found that house plants can potentially contribute to reducing indoor air pollution significantly.

The research tested three types of common houseplants found in UK homes. They included Peace Lily (Spathiphyllum wallisii), Corn plant (Dracaena fragrans), and Fern Arum (Zamioculcas zamiifolia). These plants have become a staple due to their moderate price and ease of maintenance.

Researchers put each plant in separate chambers containing Nitrogen Dioxide (NO2)—a common air pollutant—at levels comparable to an office next to a busy road. After an hour, all the plants (regardless of species) reduced about 50% of the NO2 in their respective chambers.

The plants are expected to reduce NO2 levels by 20% in a small office. As the size of the office increases, the expected reduction percentage decreases. It is important to note that the performance was not dependent on the plants’ environment (light conditions or soil conditions).

However, lead researcher Dr. Christian Pfrang noted that indoor plants reacted differently when removing other air pollutants such as Carbon Monoxide (CO) in previous studies. In this case, plant performance strongly depends on environmental factors.

Potted Plants Don't Improve Indoor Air Quality Much

A review and analysis of reported VOC removal efficiencies, published in 2019, reviews 12 other previously published scientific studies and tests 196 plants. The studies done in the lab by Waring and Cummings concluded that a small houseplant is capable of removing various toxins. Once again, researchers placed plants into chambers, this time exposing the plants to volatile organic compounds (VOCs).

One study showed that common household ivies exposed to formaldehyde could remove two-thirds of the VOC from the chamber. Waring argues that while the experimental data obtained from this and various other studies is not flawed, it cannot be translated into an actual house or office setting.

Waring then made another study considering different variables that allowed him to come closer to what a typical setting would be in a house room and judge how well plants cleaned the air.

The findings show that even though plants can clean the air, they do it at such a slow rate that they cannot compete with air purifiers or even an opened window. For example, you need 5,000 plants to effectively reduce VOCs in a 500-square apartment.

Should You Have Indoor Plants for Air Quality?

The short answer is yes, but not for the primary purpose of purifying your indoor air. Plants can improve your surroundings and contribute positively to your mental health. But to clean your indoor air, it is better to open windows (when outdoor air quality allows it) or have an air purifier.

Worried about air quality?

Monitor the Particulate Matter levels around the world with our free, real-time PurpleAir Map or join PurpleAir's mission to make air quality data accessible to everyone by investing in an air quality monitor for your home. 

Together, we can be informed and make changes in our daily habits and the community to improve air quality.