Do Plants Affect Indoor Air Pollution?

Indoor air pollution has become an increasing concern in modern homes and workplaces. With the widespread use of synthetic materials, electronic devices, and limited ventilation, indoor spaces can accumulate pollutants like volatile organic compounds (VOCs), carbon dioxide (CO2), and airborne particulate matter. Many believe that houseplants can naturally filter out these pollutants, creating a cleaner and healthier indoor environment. But is that really true?

What Makes Indoor Air Polluted?

Indoor air pollution comes from both internal and external sources. Everyday household activities such as cooking, burning candles or incense, and smoking release pollutants into the air. Additionally, outdoor pollutants can enter through open windows, chimneys, or ventilation systems, further contributing to indoor air quality concerns.

For a deeper dive into the factors that influence indoor air pollution, click here.

Why Do People Believe That Plants Purify the Air?

The widely held belief that houseplants can significantly improve indoor air quality originates from a 1989 NASA study. In this study, scientists placed plants inside sealed chambers containing various harmful gases. With a small fan circulating the air, researchers observed that the plants helped remove airborne pollutants. The study concluded that “plants can play a major role in the removal of organic chemicals from indoor air.”

This research quickly gained traction, becoming a popular reference point for those advocating for indoor plants. Over time, the idea solidified into common knowledge, shaping public perception for the next three decades.

So, Is It Really True?

While many embraced NASA’s findings, some researchers remained skeptical. Concrete evidence challenging the study didn’t emerge until 2019, when Michael Waring and Bryan Cummings from Drexel University published their research titled "Potted plants do not improve indoor air quality: a review and analysis of reported VOC removal efficiencies." Their study analyzed twelve previously published experiments on the ability of plants to clean the air.

One experiment found that household ivy exposed to formaldehyde could remove two-thirds of the VOCs in a controlled setting. Though encouraging, Waring and Cummings argued that these results do not translate to real-life home or office environments—similar to the limitations of the original NASA study. They found that most experiments relied on highly controlled conditions that do not reflect how air circulates in typical indoor spaces.

So, does this mean all these studies were wrong? Not necessarily; plants definitely do have the ability to clean the air to some degree. However, Waring calculated that under real-world conditions, plants remove pollutants at an incredibly slow rate—far less efficiently than an air purifier or even an open window. According to his findings, it would take anywhere from 10 to 1,000 plants per square meter of floor space to match the air-cleaning capacity of a building’s ventilation system or a few open windows.

Does This Mean I Shouldn't Keep Plants Indoors?

Even if plants don’t significantly purify the air, they still offer many benefits. Research has shown that having plants indoors can positively impact mood, reduce stress, and even lower blood pressure. A 2022 study found that incorporating plants into indoor workspaces contributed to improved well-being and reduced stress levels.

So, while your plants might not be the air-cleaning powerhouses you hoped for, they still add beauty, serenity, and mental health benefits to your space. Keep your plants—just don’t rely on them as your primary method for improving indoor air quality!

This blog was originally published in 2022, and updated in 2025 for freshness