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The common belief that houseplants are an effective way to clean the air in your home stems from NASA research published in 1989 that concluded houseplants possess the unique ability to filter toxic chemicals from the air. While plants do filter volatile organic compounds (VOC) from the air, the research was limited to enclosed environments and is not easily translated to practical use in the home.
More recent research published in the Journal of Exposure Science & Environmental Epidemiology (2020) reviewed 12 published studies on the rate and efficiency of plants to filter VOC from the air and uncovered a vital flaw in the common interpretation of the initial studies. Because the previous studies were performed in an enclosed chamber, the results do not translate directly to the use of plants to filter the air in indoor environments and do not adequately address the impact of plants on indoor air quality in homes and offices.
While plants do filter the air, they do so at too slow a rate to use them as a substitute for air filters or air purifiers. The number of plants needed to offset the natural air exchange in homes and offices may exceed 10 plants per square foot of living space. That amounts to 1,200 plants (or more) in a 10’ by 12’ room. This makes trying to use houseplants to filter the air in your home impractical, but they can be used to supplement other efforts.
Do plants filter indoor air?
Plants do filter indoor air and can be effective in removing VOC from the air. However, they do so at a much slower rate than previously believed. Because most of the air in your home or office is replaced by air that infiltrates from the outside and is often completely exchanged every hour, the effects of plants filtering indoor air are minimal at best, explains Harvard University.
Plants can certainly be used to promote healthy indoor air quality but should not be relied on to filter the air like an air filter or air purifier. It would simply take too many plants to get the job done. Using them as a supplemental way to improve your indoor air quality may be a reasonable solution.
Which plants are best for filtering the air?
Some plants filter the air better than others. The following plants, identified by NASA, are thought to be the most effective, but keep in mind that even the most effective plants cannot filter the air in your home on their own.
Spider Plant (Chlorophytum comosum)
This easy-to-grow plant is both beautiful and beneficial for helping to keep the air clean in your home. Its dramatic arching leaves and propensity to develop new baby spiders on long cascading stems make the spider plant a striking addition to the home or office. Hung in a sunny window, a spider plant will put on quite a show and aid in keeping the air clean in your home.
English Ivy (Hedera helix)
English Ivy is a vining plant that can be grown in hanging baskets or placed on dividers and bookcases and allowed to trail over the sides. It can even be grown on a trellis or trained on round or heart-shaped supports to create a living wreath. It prefers bright light, but will grow in low light. But beware. Variegated varieties will lose their dramatic variegated foliage if the plant does not get enough light.
Philodendron (Philodendron sp.)
Like the English Ivy, philodendrons produce long, cascading vines that can be allowed to flow over the sides of pots or trained to climb trellises. These plants have thick, waxy leaves that may be solid green or variegated. Philodendrons grow in low light but may lose their variegation if they do not receive some bright light during the day.
Boston Fern (Nephrolepis exaltata ‘Bostoniensis’)
Boston ferns produce traditional frilly fronds and add tropical air to your home or office, but they can be finicky, especially in the winter when the air inside your home is dry. They are traditionally grown in baskets to show off the delightfully lacy foliage. Boston ferns need humid air and indirect light. They do well near northern or eastern windows.
Peace Lily (Spathiphyllum)
The peace lily is a delightful plant with large, deep green foliage and attractive white flowers. These flowers are actually bracts that form a hood over the tiny yellow flowers in the center. Peace lilies are easy-to-grow and don’t require a lot of light, making them suitable for offices and low-light areas. They do best with some bright indirect light but will adapt to less. Peace lilies grown in low light may not bloom.
Snake Plant (Sansevieria trifasciata)
The snake plant produces stiff lance-like leaves that range in color from solid green to variegated varieties. Most feature a yellow border. Depending on the variety, they vary in height from a mere six inches to towering plants that reach 8 feet tall. This plant thrives with a few hours of bright indirect light a day but will survive in less light.
Chinese Evergreen (Aglaonema modestum)
As a foliage plant, the Chinese Evergreen brightens dark corners and brings life to the room. Its striking foliage varies from solid green to impressive leaves mottled with green or yellow. Chinese Evergreen prefers some indirect light but will grow in low light. This plant is tolerant of some neglect and is perfect for those who do not have a green thumb.
Aloe Vera (Aloe vera)
Aloe Vera is a succulent with thick spikey leaves that store water. It is most known for the healing properties of the thick gel inside the leaves, often used as a natural remedy for burns and skin abrasions. But it is a striking plant on its own. Aloe Vera likes a sunny location and requires very little care.
Promising New Houseplants for Filtering Indoor Air
Researchers from the University of Washington have recently genetically engineered the pothos ivy to remove hazardous compounds, such as chloroform and benzene. In tests conducted in enclosed chambers, the newly engineered version of the pothos ivy removed 82 percent of chloroform from the air in three days and 75 percent of the benzene in eight days. The unmodified pothos ivies did not filter out chloroform or benzene.
At the current time, using the engineered pothos ivy as an air purifier in the home comes with some drawbacks. The plant must be placed in an enclosed area, and air must be circulated around the plant with a fan. It is unknown how quickly or effectively the engineered pothos vine will filter the air in homes and offices.
More research is being done to enhance the plant’s ability to remove formaldehyde from the air. These genetically engineered plants are not available to the public at this time but do show promise for the future.
Are plants good for people with asthma and allergies?
It has long been believed that plants are good for people who suffer from asthma and allergies because plants filter volatile organic compounds from the air. However, the number of plants needed to make a noticeable difference in the air quality in your home or office suggests that adding plants to the home or office may not improve the air quality sufficiently to make an impact on asthma and allergies.
In addition, plants do not remove common asthma and allergy triggers such as pet dander, dust, and pollen from the air.
For some people with asthma and allergies, keeping houseplants in the home or office may actually make things worse. Potting soil often contains mold, especially if plants are overwatered, and may trigger asthma and allergies. Likewise, blooming plants release pollen into the air and may complicate asthma and allergy symptoms.
Growing foliage plants and using care to prevent overwatering and consequent mold growth may be beneficial to those with allergies and asthma as they will filter out some of the offending chemicals from the air.
Do plants add oxygen to the air?
Most plants absorb carbon dioxide during photosynthesis and release oxygen into the air during the day. At night, the process reverses, and they give off carbon dioxide during respiration. That means they can increase oxygen in the air during the day but also increase carbon dioxide at night. This makes them beneficial for adding oxygen to your home during the day but unsuitable for bedrooms or sickrooms due to the release of carbon dioxide at night.
Some plants, however, do release oxygen at night, making them ideal for bedrooms and sickrooms. These include epiphytic bromeliads, orchids, and succulents. Add them to the bedroom to refresh the air with oxygen at night.
The common belief that plants absorb carbon dioxide and release oxygen all the time leads to the misconception that plants in bedrooms and sickrooms improve the air quality and provide copious amounts of oxygen to the inhabitants. While some, like those above, do provide fresh oxygen at night, the vast majority of plants do not.
How do Volatile Organic Compounds (VOC) get in the air?
VOCs are a group of chemicals commonly found in building supplies, carpeting, home furnishings, and cleaning or household supplies. They are present in the material when you bring them into your home. Once installed, the chemicals are released (off-gassed) into the air over time.
Some VOCs enter the air when you use aerosol air fresheners or other cleaning supplies. Even scented candles can release VOCs into the air when they are burned. These tiny particles are too small to be trapped in traditional air filters.
According to the EPA, the level of Volatile Organic Compounds inside the average American home is 2 to 5 times greater than the VOC levels outside. It can reach a level of 1,000 times higher than outside levels for several hours after household activities, such as stripping paint.
There are no federal standards or guidelines indicating an acceptable (and safe) level of VOCs in the home, explains the EPA.
What are effective ways to remove VOCs from indoor air?
You can do several things to reduce the Volatile Organic Compounds in the air.
- Add houseplants known to filter VOCs from the air. Although they won’t do the job on their own, they will enhance the beauty of your home and will assist in removing offending chemicals from the air.
- Limit your use of cleaning products, paint strippers, and other products that release VOCs in the home. Use non-aerosol versions when practical.
- Keep your home well ventilated, particularly when using paint thinners and strippers.
- Store unused products in the garage or shed to prevent them from leaking into your indoor air.
- Buy floor models of new furniture or carpets as they tend to release fewer VOCs over time. Those that have already been exposed to the air are likely to emit fewer toxins into your home.
Houseplants have long been thought to be natural air purifiers for the home, but this is only partially true. Many do an excellent job of filtering VOCs from the air, but they do so at such a slow rate that using them as your only source for air filtering is not practical. They can, however, be used in conjunction with other measures to help keep the air in your home clean.
In addition, houseplants provide several benefits beyond filtering the air. They remove carbon dioxide, release fresh oxygen, release moisture into the air, and improve overall health by lowering anxiety, lessening fatigue, and even reducing the need for pain medications. Some studies report decreased rates of sickness in office settings with plants as opposed to offices without plants.