Air Purifying Plant Numbers – How Many Plants For Clean Air Indoors
By: Raffaele Di Lallo, Author and founder of Ohio Tropics houseplant care blog
Houseplants have long been known to purifyour toxic indoor air. How many houseplants do you need to purify yourindoor air? Keep reading to find this out, and more!
Air Purifying Plant Numbers
There was a famous NASA study that was conducted back in1989 that found that many houseplants are able to remove many toxic and cancercausing volatile organic compounds from our indoor air. Formaldehyde andbenzene are two of these compounds.
Bill Wolverton, the NASA scientist who conducted this study,provided some insight into the number of plants per room that you would need tohelp purify indoor air. Although it is difficult to say exactly how many plantsare needed to purify indoor air, Wolverton recommends at least two good sizedplants for every 100 square feet (approximately 9.3 square meters) of indoorspace.
The bigger the plant and leafier the plant, the better. Thisis because air purification is influenced by the surface area of leavespresent.
Another study, funded by Hort Innovation, found that evenjust one houseplant in an average room (4 meters by 5 meters room, or roughly13 by 16 feet) improved air quality by 25%. Two plants produced a 75% improvement.Having five or more plants produced even better results, with the magic numberbeing 10 plants in a room of the size previously mentioned.
In a larger room (8 x 8 meters, or 26 by 26 feet), 16 plantswere needed to provide a 75% improvement in air quality, with 32 plants producingthe best results.
Of course, all of this will vary on the size of the plant.Plants with more leaf surface area, as well as larger pots, will produce thebest results. Bacteria and fungi in the soil actually use broken down toxins,so if you can expose the surface of your soil in your potted plants, this canaid in air purification.
Plants for Clean Air Indoors
What are some of the best plants for clean air indoors? Hereare some of the good options that NASA reported in their study:
- Golden Pothos
- Dracaena (Dracaena marginata, Dracaena ‘Janet Craig,’ Dracaena ‘Warneckii,’ and the common “corn plant” Dracaena)
- Ficus benjamina
- English Ivy
- Spider Plant
- Philodendrons (Philodendron selloum, elephant ear philodendron, heart leaf philodendron)
- Chinese Evergreen
- Peace Lily
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Without proper ventilation, it doesn’t take long for indoor pollutants to build up to unhealthy levels. Here are some of the best air-purifying houseplants that can clean the air in your home!
Indoor pollutants come in two major varieties—particulates such as dust, mold spores, and pollen, and volatile organic compounds ( VOC s). VOC s are gases that are released from paints, fabrics, wallpaper, carpeting, plastics, and solvents commonly found in most homes. Even household chemicals such as bleach, ammonia, detergents, furniture polish, carpet cleaners, and moth balls give off harmful gases. Mechanical or electrostatic filters can be effective in trapping particulates, but unless we remove the source, airborne chemicals are difficult to eliminate entirely.
Clean the air with houseplants
We all know that basic bit of botany: plants absorb carbon dioxide and release oxygen during photosynthesis. Outdoors, tree planting makes use of that concept to atone for the effects of air pollution, but what about our indoor air quality?
Years ago, NASA studied ways to provide fresh air in enclosed spaces and tested 19 different species of plants to see if they would be effective at cleaning the air. They found that in just 24 hours, up to 87% of the formaldehyde, benzene, and trichloroethylene was removed from the air by the leaves and roots of the plants, while oxygen was returned to the room.
The best news is that the most effective toxic avengers are common, low-light houseplants!
Best air-purifying Houseplants
Some of the best plants for indoor air cleaning are:
- English ivy (Hedera helix) is a popular, hardy plant that is easy to grow. It removes most pollutants. It is not fussy about light and can survive sun to shade. Ivy doesn’t like high temperatures and prefers to stay cool. Keep moist and spray the leaves weekly to discourage spider mites.
- The Peace Lily (Spathiphyllum sp.) is a beautiful plant with a lovely white flower which thrives nicely in average indoor temperatures. Peace lilies are known to clean the air of alcohols, acetone, trichloroethylene, benzene, and formaldehyde. Keep moist in a semi-shady location.
Peace lily flower
- Varigated Snake Plant (Sansevieria trivasciata), also called “Mother-in-Law’s Tongue,” is very easy to grow. Water heavily then let it dry out before watering again. It can survive any location from sun to shade.
Snake plant (this 35-year-old Mother-in-Law’s Tongue actually did come from a mother-in-law).
- Spider Plants (Chlorophytum comosum) are very easy to grow. Keep moist in a semi-sunny to shady spot and it will thrive.
- Bromeliads win a gold star for cleaning up most pollutants. They release oxygen and remove air pollutants at night while you sleep! These pretty plants with their bright flowers and green foliage do best with bright, indirect sunlight or fluorescent office lighting. This drought-tolerant plant doesn’t need much maintenance and will get root rot if you over-water or don’t provide good drainage.
- Dracaena like to be kept moist in a semi-sunny to shady location. Warneck, Janet Craig, red-edged, and cornstalk dracaenas have been rated the highest in removing air pollutants.
- Weeping fig(Ficus benjamina) likes bright indirect light, high humidity, and warm temperatures. Water when top of soil feels dry and mist the top regularly.
- Rubber plants tolerate dim light and cool temperatures and remove air toxins from any indoor environment.
- Golden pothos or “Devil’s ivy” likes a warm location in bright, indirect light. Let it dry out between waterings.
- Areca palmsChrysalidocarpus lutescens, are beautiful, easy plants that remove all indoor air toxins.
- Philodendrons are practically bullet-proof plants. They can take full sun to shade if watered regularly. Heart-leaf, Philodendron selloum, and elephant ear philodendrons are the best air cleaners.
- If you would rather have flowering plants, two that fared well in the testing were Chrysanthemums and Gerberadaisies. They are effective at removing VOC s and produced blossoms too!
- Chinese evergreens(Aglaonema) like warm temperatures and medium to low light conditions. Allow it to dry a bit between waterings. Keep out of drafts, which can cause the leaves to brown.
- Reed or Bamboo Palms thrive in low light as long as it is kept evenly moist.
- Other great air-purifying houseplants include Boston ferns, aloe vera, and bird of paradise.
No need to turn your home into a jungle, though: in a house with 8 to 9 foot high ceilings, only one or two plants per 100 square feet of floor space are recommended for maximum benefit. The roots and micro-organisims in the soil play as important a role as the leaves, so plants should be in 6 to 8 inch wide pots with the soil surface exposed to the air. Soaking up toxins seems to have no adverse effect on the plants studied. Research shows that they safely metabolize the compounds by breaking them down to harmless carbon, water, and salts.
We clean our homes of dirt so why not clean the air, especially if it is as easy as adding a few more houseplants.
See our Houseplants Care Guide on how to keep your houseplants happy and healthy—so that that they can keep your air healthier, in turn!
Since there’s no definite conclusion if the plants clean the air or not. In what way do you think plants are still healthy for indoor air?
Nell Foster says
Hi Michelle – That was my point in doing this post. The tests haven’t been done in a home environment. Plants take in CO2 & give off O2 but you can’t expect a 6″pothos to clean a whole room. In my opinion, houseplants are healthy because they bring something living (besides us!) into our homes – it’s the happiness factor. Nell
Hi Nell! Thanks for the time to investigate this subject! I’m doing to same right now and have always been sceptical. However, there is a University in the Netherlands that is doing research in actual living spaces, like a retirement home and offices. No conclusions yet, but I’m very curious about the results.
Nell Foster says
Iris – Thank you for sharing that link! I was unaware that there’s a study going on & look forward to seeing what they find. I’m going to check in on the final results. Nell
Karen Olson says
Nell, excellent article. While it’s difficult to measure the exact amount of plants needed per square foot of housing to produce the right amount of oxygen, I agree with you. We know that we need oxygen and plants need carbon dioxide. Having plants and caring for plants makes me happy and healthy. And plants add color and decoration to a home or office. These are all good reasons to have plants.
Nell Foster says
Thank you Karen! This study was done in controlled chambers which are nothing like our homes. Plants do take in the bad & give off oxygen but we can’t expect to rid our living room of formaldehyde. I love them because they make my soul smile & my home look great. Sounds like it’s the same for you! Nell
Christmas cactus plants are green succulents with bright red flowers that bloom at Christmas time. They are easy to care for and highly drought-tolerant. While they make a cheerful holiday gift, they are also functional plants. These succulents release oxygen during the night, instead of during the day like most other plants, according to information published by Beyond Jane.
- Spider plants are especially handy at removing formaldehyde from the air, according to information published by Colorado State University.
- They also produce oxygen and plenty of plantlets--baby spider plants that dangle like stars at the end of the long, slender leaves.