The NASA Clean Air Study: How Plants Clean the Air

By: Evan Scoboria, Last updated: June 12, 2023

In 1989, NASA conducted a significant study that has since become a staple reference when talking about the purification properties of plants. The study, NASA’s Clean Air Study, was carried out to discover sustainable ways to clean the air in space stations. The research aimed to identify which, if any, houseplants could help reduce air pollutants in closed, air-tight spaces. The conclusions drawn from this innovative research provide practical insights adopted in many indoor environments, from homes to office buildings. This article dives into the details of NASA’s Clean Air Study, its key findings, and the science behind how plants purify the air. We also discuss the application of these findings in our daily lives and address some limitations and criticisms of the study. Ultimately, understanding this study can provide us with tools to improve the air quality we breathe daily.

The NASA Clean Air Study: How Plants Clean the Air

The Importance of Clean Air in Space Stations

Maintaining clean air within space stations is of paramount importance for a variety of reasons. The environment within a space station is tightly sealed and meticulously controlled, making air purification a critical component of maintaining a habitable atmosphere.

Limited Fresh Air Supply: Unlike on Earth, where the air is abundant and continuously refreshed, space stations operate in a vacuum without accessible fresh air. Consequently, the air within a space station is continually recycled. Without proper cleaning mechanisms, it can quickly become polluted with chemicals, bioeffluents (human metabolic waste like CO2 and perspiration), and other harmful particles.

Off-gassing from Synthetic Materials: The construction of space stations heavily relies on synthetic materials, many of which have been found to off-gas pollutants into the enclosed environment. This release of volatile organic compounds (VOCs) is a significant concern for air quality on space stations, with possible long-term effects on astronauts' health.

Physical and Mental Health: Clean air is essential for maintaining the physical health of astronauts. Poor air quality can lead to various health problems, including respiratory issues, allergies, and more serious diseases over time. Moreover, knowing that the air is clean and safe can contribute positively to the mental well-being of those living in a space station's confined and isolated environment.

Performance and Safety: Air quality can also impact cognitive function and overall performance. Astronauts are required to perform complex tasks that require high levels of concentration and precision. Poor air quality could negatively affect their ability to perform these tasks and may increase the risk of errors, with potentially severe consequences.

For all these reasons, air purification on space stations is a critical research topic, with studies like NASA's Clean Air Study contributing significantly to our understanding of how to sustain clean air in such unique environments.

Key Findings of the Study

The NASA Clean Air Study, conducted over two years from 1989 to 1990, resulted in several critical findings related to indoor air purification. These findings significantly affect air quality in space stations and indoor environments here on Earth. Here are the fundamental discoveries:

The Ability of Plants to Purify Air

Thanks to their natural photosynthesis process, plants have a unique capacity to purify the air. This process involves carbon dioxide intake and oxygen release, which improves air quality by increasing oxygen content. However, NASA's Clean Air Study discovered that certain plants go beyond this primary process and can eliminate significant amounts of specific toxins, such as benzene, formaldehyde, and trichloroethylene, from the air.

This toxin absorption occurs because plants are efficient absorbers, and their roots and associated microorganisms play a significant role in neutralizing volatile organic compounds (VOCs). The plant pulls polluted air down to its roots, where these compounds are converted into food for the plant and its root-dwelling microbes. This activity demonstrates the symbiotic relationship between plants and microbes and underscores the power of this relationship for air purification.

Moreover, this study also discovered that some plants have higher purification capabilities than others. For example, Peace Lily and English Ivy effectively removed multiple toxins. This shows that, along with beautifying our living spaces, certain indoor plants can play a crucial role in enhancing the air quality we breathe.

Plant-Soil Microorganism Interactions

Plant-soil microorganism interactions are an integral part of the ecosystem, with plants and soil microorganisms forming a symbiotic relationship that is essential for both health. These interactions play a crucial role in nutrient cycling, decomposition of organic matter, and disease suppression, among other functions.

Soil microorganisms, which include bacteria, fungi, protozoa, and nematodes, interact with plant roots in the rhizosphere - the soil region directly influenced by root secretions and associated soil microorganisms. These microorganisms can enhance nutrient uptake by plants, helping them to thrive.

For instance, certain bacteria, known as rhizobia, can form nodules on the roots of leguminous plants and fix nitrogen from the atmosphere, making it available to the plant. In return, the plant supplies the rhizobia with sugars, providing energy. This symbiotic relationship benefits the plant and bacteria involved and enhances soil fertility by increasing nitrogen content.

Similarly, mycorrhizal fungi form symbiotic relationships with many plant species. These fungi colonize the plant roots, extending their network of hyphae into the surrounding soil, which increases the plant's access to nutrients and water. In return, the fungi receive sugars from the plant, helping them to grow.

Best Air-Purifying Plants

  1. Spider Plant (Chlorophytum comosum): Known for its ability to tolerate low light conditions, the spider plant is excellent at purifying the air of benzene, formaldehyde, carbon monoxide, and xylene.

  2. Snake Plant (Sansevieria trifasciata): This plant, also known as mother-in-law's tongue, filters out formaldehyde, which is common in cleaning products, toilet paper, and personal care products.

  3. Boston Fern (Nephrolepis exaltata): This plant has a lush, pleasing aesthetic and works hard to remove formaldehyde and xylene from the air.

  4. Peace Lily (Spathiphyllum): This plant effectively cleans the air of ammonia, benzene, formaldehyde, and trichloroethylene. However, it should be noted that peace lilies can be toxic to pets if ingested.

  5. English Ivy (Hedera helix): This vigorous grower fights off airborne toxins, including benzene, formaldehyde, and trichloroethylene.

  6. Bamboo Palm (Chamaedorea seifrizii): Also known as the reed palm, this plant is a superstar at filtering out formaldehyde. It's also pet-friendly!

  7. Philodendron: This fast-growing vine is adept at absorbing formaldehyde. However, they are toxic to pets, so they're best for households without furry friends.

  8. Aloe Vera: Besides helping treat burns, aloe vera also helps remove formaldehyde and benzene from the air.

Feasibility of Bioregenerative Life Support Systems

Bioregenerative life support systems (BLSS) represent a possible solution for long-term space missions where resupply is impractical. They involve using biological processes and organisms to recycle waste, produce food, and maintain air and water supplies. Despite these systems' promise, their feasibility depends on a range of factors, including technology, resources, and the duration and nature of the mission.

One of the primary challenges is the technological complexity required to create a stable, self-regulating environment that can support human life over long periods. This includes balancing oxygen and carbon dioxide levels, managing waste, producing food, and maintaining ideal humidity and temperature conditions. Achieving this balance is technically challenging and requires a significant understanding of biological and ecological systems.

Moreover, the space and resource requirements for a BLSS are substantial. For instance, producing sufficient food for a crew through farming requires considerable space and resources, including water, nutrients, and light. It's also worth considering the psychological impact of living in a closed system for extended periods, which could have detrimental effects on the crew's well-being.

While there has been progress in this area – for example, the 'Biosphere 2' project and experiments conducted by the Chinese Lunar Palace 1 – it's clear that a fully functional, long-term BLSS is still many years away. More research and technological advances are needed to make such systems feasible for sustaining life in space.

Overall, the feasibility of bioregenerative life support systems is an exciting concept, representing a significant step towards sustained human presence in space. However, it's clear that their successful implementation hinges on overcoming substantial technological, logistical, and psychological challenges.

Understanding the Science: How Plants Clean the Air

Plants possess a unique mechanism that allows them to clean the air around us, a process that is intrinsically linked to their nature. It's all tied to photosynthesis - the process through which plants convert carbon dioxide into oxygen. But there's more to it than just producing oxygen and removing carbon dioxide.

When plants undergo photosynthesis, they absorb sunlight through their leaves and use this energy to convert carbon dioxide and water into glucose - a type of sugar that plants use for energy - and oxygen, which is released back into the air.

During this process, plants absorb airborne pollutants on their leaves through the tiny pores known as stomata. They can pull in volatile organic compounds (VOCs) like benzene, formaldehyde, and trichloroethylene – common contaminants in our indoor air. Once inside the plant, these compounds are transported to the roots, where soil microorganisms break them down into safer compounds, a process known as phytoremediation.

Another way that plants help clean the air is through a process called transpiration. As plants release water vapor from their leaves, they also increase the humidity in their environment. This increased moisture can help keep dust and other airborne pollutants from circulating.

However, it's important to note that while plants can improve indoor air quality, they are not substitutes for proper ventilation and air filtration. The effect of a few houseplants in a typical home or office environment is relatively small compared to these other factors.

Still, the benefits of indoor plants go beyond air purification. They can also improve mental well-being, reduce stress, and increase productivity - making them a great addition to any indoor space.

Applying the Findings: Using Plants for Air Purification at Home

NASA’s Clean Air Study provides a solid foundation for using indoor plants as natural air purifiers. Incorporating this knowledge at home can significantly enhance the air quality in your living spaces, providing cleaner air and a more tranquil and aesthetically pleasing environment. Here's how you can apply these findings in your home.

Choose the Right Plants: Based on NASA’s study, some plants are more effective at removing certain pollutants than others. For instance, spider plants and Boston ferns are great at removing formaldehyde, while peace lilies excel at filtering benzene and trichloroethylene. So, selecting the right plants based on the potential pollutants in your home can make a difference. Remember, most indoor plants are tropical, so they'll need temperatures between 60 and 75 degrees Fahrenheit to thrive.

Ensure Proper Care: Plants can only purify the air effectively if they're healthy and well cared for. Ensure they have the right light, water, and humidity for their specific species. Also, clean their leaves regularly to ensure they can effectively absorb sunlight and air pollutants.

Place Plants Strategically: To maximize the air purification effect, place plants in areas where you spend most of your time, like the living room, bedroom, or home office. Also, consider placing them in areas with higher pollutant levels, like the kitchen or bathroom.

Use Enough Plants: The NASA study recommended having at least one plant per 100 square feet of space for effective air cleaning. So, you'll need more plants if you have a larger home.

Keep Plants Healthy: Remember, a sick or infested plant can become a source of pollutants. Regularly check your plants for any signs of disease or pests, and address any issues promptly to keep them healthy and effective at cleaning the air.

While NASA's Clean Air Study offers valuable insights, it's also important to remember that plants alone can't fix serious air quality issues. If you're dealing with high pollutant levels, it may be necessary to take additional steps like improving ventilation, reducing the sources of pollutants, or using air purifiers. But indoor plants can be an excellent option for general wellness and boost air quality.

Limitations and Criticisms of the Study

While NASA’s Clean Air Study has provided groundbreaking insights into the capabilities of indoor plants to purify the air, it is not without limitations and criticisms. It’s essential to view the study’s findings within the proper context and consider some of the following points.

Study Conditions vs. Real Homes: The conditions under which the NASA study was conducted do not precisely mirror conditions in the average home. The study was performed in controlled, sealed environments to test for specific pollutants, unlike the myriad of factors in a typical home environment.

Removal of Gaseous Pollutants: While the study demonstrated that plants could remove certain gaseous pollutants, the rate at which they do so may not be significant enough to make a substantial difference in overall air quality, especially in larger or poorly ventilated spaces.

Overemphasis on Certain Pollutants: The study focused on indoor pollutants like benzene, formaldehyde, and trichloroethylene. However, many other contaminants are found in homes, like dust, mold spores, and carbon monoxide, which the study did not address. Plants may not effectively remove these.

Potential Health Risks of Indoor Plants: While plants can remove certain toxins, they can also introduce mold and pollen into the air, potentially worsening air quality for individuals with allergies or respiratory conditions. Furthermore, certain plants may be toxic if ingested by pets or children.

Inadequate Replacement for Ventilation: Some critics argue that the study may encourage people to rely too heavily on plants for air purification when proper ventilation and source control of pollutants are far more effective strategies for improving indoor air quality.

Despite these limitations, NASA’s Clean Air Study findings continue to help understand plants' role in improving indoor air quality. However, it’s essential to consider other air-cleaning strategies and to maintain a balanced view of the capabilities and limits of indoor plants as air purifiers.

Future Research and Innovations in Air Purification

As we look towards the future, the field of air purification continues to evolve with new research and innovations that aim to create healthier indoor environments.

Smart Air Purifiers: Advancements in technology have led to the development of smart air purifiers that can monitor and control air quality using real-time data and automation. These devices can connect to your smartphone or home automation system, providing alerts when air quality decreases and automatically adjusting settings based on current conditions.

Bio-based Air Purifiers: Scientists are exploring bio-based solutions for air purification inspired by NASA's Clean Air Study. Some innovators are developing systems that integrate plants and microorganisms with traditional filtration technologies to remove pollutants effectively.

Air Purifying Building Materials: Research is also underway into building materials and paints that can purify the air. Some materials use photocatalytic reactions activated by light to break down pollutants, while others may use bio-based materials, like moss or algae, that can absorb impurities.

UV-C Light Technology: Another promising technology is UV-C light, which can eliminate bacteria, viruses, mold, and other harmful microorganisms from the air. However, while this technology has been used in medical settings for years, further research is needed to make it safe and effective for general indoor use.

Plasma Air Purifiers: These devices use ionization technology to purify the air. By creating a plasma field and releasing ions into the air, they can neutralize harmful substances like bacteria, viruses, and volatile organic compounds (VOCs). More research is needed to validate the safety and effectiveness of this technology.

While these advancements are exciting, it's important to remember that they should be considered as part of a comprehensive approach to indoor air quality. Measures such as adequate ventilation, controlling sources of pollution, and maintaining a clean environment will always be essential components of healthy indoor air quality.

Frequently Asked Questions

What was the primary goal of NASA's Clean Air Study?

The primary goal of NASA's Clean Air Study was to find effective ways to purify the air in space stations, creating a healthier environment for astronauts. They investigated how plants could remove volatile organic compounds from the air, potentially harmful pollutants often found indoors.

According to the study, Which plants most effectively purified air?

The study identified several plants as effective air purifiers. These include the Peace Lily, English Ivy, Spider Plant, Bamboo Palm, and various types of Ferns and Dracaenas.

Can I purify the air in my home using just plants?

While plants can contribute to cleaner air in your home, they are not a substitute for adequate ventilation, controlling sources of pollution, and maintaining a clean living environment. It's best to think of plants as complementary to these essential measures.

Has there been any criticism of NASA's Clean Air Study?

Yes, there has been some criticism of the study. One main point is that the study was conducted under controlled laboratory conditions, which don't necessarily replicate real-world indoor environments. Furthermore, the study didn't address the many plants needed to purify the air in a typical home significantly.

What future research and innovations are there in air purification?

Current research in air purification explores various innovative approaches, including smart air purifiers, bio-based air purifiers, air-purifying building materials, UV-C light technology, and plasma air purifiers. These technologies are still under development and require further research to validate their safety and effectiveness.


In conclusion, NASA's Clean Air Study has significantly contributed to our understanding of indoor air purification. The study, which originated from a need to maintain clean air in the closed environments of space stations, shed light on the remarkable capabilities of several common houseplants to remove harmful pollutants from the air.

However, it's crucial to note that while these plants can support a healthier indoor environment, they cannot wholly replace other necessary measures such as proper ventilation, pollutant source control, and regular cleaning. Furthermore, applying the study's findings in real-world conditions has limitations, considering the large number of plants required to improve air quality in a typical home significantly.

Yet, the Clean Air Study sparked interest and opened avenues for further research in air purification. Future innovations, from smart air purifiers to air-purifying building materials, promise exciting developments in this field. By leveraging nature's solutions and technological advancements, we can strive to create healthier indoor environments for all.

References and Further Reading 

  1. Wolverton, B. C., Johnson, A., & Bounds, K. (1989). Interior landscape plants for indoor air pollution abatement. NASA.

  2. B. C. Wolverton, Rebecca C. McDonald, and E. A. Watkins, Jr., "Foliage plants for removing indoor air pollutants from energy-efficient homes," Economic Botany, vol. 38, no. 2, pp. 224–228, 1984.

  3. Orwell, R. L., Wood, R. L., Tarran, J., Torpy, F., & Burchett, M. (2004). Removal of benzene by the indoor plant/substrate microcosm and implications for air quality. Water, Air, and Soil pollution, 157(1), 193-207.

  4. "Improving Indoor Air Quality." EPA, Environmental Protection Agency, 19 April 2021,

  5. Pegas, P. N., Alves, C. A., Evtyugina, M. G., Nunes, T., Cerqueira, M., Franchi, M., ... & Pio, C. (2012). Could houseplants improve indoor air quality in schools? Journal of Toxicology and environmental health, Part A, 75(22-23), 1371-1380.

  6. Lu, C., Deng, Q., Li, Y., Sundell, J., & Norbäck, D. (2016). Outdoor air pollution, meteorological conditions, and indoor factors in dwellings in relation to sick building syndrome (SBS) among adults in China. Science of The Total Environment, 560, 186-196.

  7. "The Appearance of Indoor Plants and their Effect on People's Perceptions." Green Plants for Green Buildings. Accessed on 8 June 2023,