There is a lot of talk about improving the air quality of a home by having houseplants to clean the air. While houseplants have purifying capacities, if it is feasible to clean indoor air solely with houseplants is questionable.
Research shows that significant improvement of indoor air quality with houseplants requires 100 – 1000 plants per 10 square feet. Plants clean the air by filtering carbon dioxide and toxins through leaves and roots. Indoors, frequent air exchange and small plant size reduce the filtration effects of plants.
Read all about plants’ capacities to filter out toxins and pollutants from the air we breathe and which five purifying plant species are my favorites.
How Many Plants for Clean Air per Living Area?
100 – 1000 Plants Per 10 Square Feet (1 m2) Are Required
Now, even though plants do actually clean air, many scientific studies show that the effect on indoor air quality by houseplants is so small that it is almost immeasurable.
The most famously cited study that proves how indoor plants purify the air is the NASA 1989 study. NASA recommends one plant every 100 square feet (9.2 m2). This means that for a big house, 15 – 18 plants would be enough.
If you want to understand how NASA did its experiments, I found this great Youtube video that explains it wonderfully:
The NASA experiments put the plants in small hermetically sealed chambers to measure the plants’ purifying effect. In reality, though, no living space is sealed that way and there is also much more air to be filtered than in a tiny chamber. Later studies, such as Cummings & Waring in their paper “Potted plants do not improve indoor air” (2020), therefore explain where NASA went wrong and propose new numbers of plants that are more accurately describing real-life situations.
Let me give you the exact number of plants needed to clean the air of a household. Cummings & Waring (2020) mention in their study that for 10 square feet on average 100 – 1000 houseplants are needed. Here’s what those numbers look like for average living areas:
| Housing Type | Average Size | Number of Plants |
|---|---|---|
| Single Room | 15 m2 / 161 sq. feet | 1’600 – 16’000 Plants |
| House | 200 m2 / 2150 sq. feet | 21’500 – 215’000 Plants |
The bigger the plants, the less you would need. But considering even the lowest numbers needed to make a measurable difference in the air quality of about 1’600 plants per room, you can see that it is somewhat futile to try to achieve this.
Why Is There No Significant Improvement Even Though Plants Are Purifying Experts?
Why are plants unable to significantly improve indoor air quality, given their immense filtration capacities? Here’s why:
- Our homes are not hermetically sealed
- Frequent air exchange brings in new pollutants
- Plants have a slow filtration process
- High amounts of toxins exceed houseplants’ capacities due to their small foliage surface
Our households though are far from being hermetically sealed from the outside world. Rather, air exchanges happen frequently – through doors, windows, and bad insulation – and the rate at which your houseplants filter out pollutants is too slow to make up for that exchange. Especially considering the large number of pollutants in most urban or semi-urban living areas and given the rather small size of most houseplants, they simply can’t deal with so much pollution.
Nevertheless, scientific inquiries on the benefits of plant purification processes in indoor areas are continued. In the face of crises such as the Covid-19 pandemic, scientists look to plants for new and eco-friendlier alternatives to improve air quality and reduce the harmful micro-components within it. It might well be that future research shows new findings and strategies.
Personal Note: Even though the majority of current scientific evidence doesn’t seem to support the fact of improved air quality due to indoor plants, as for myself I have made great experiences with plants in my home. Having to respect my plants’ needs such as higher humidity in winter or light throughout the day makes my home better for me, too. A room filled with plants just has a very different quality to it.
Do Houseplants Really Purify Air?
Cummings & Waring might be right about the fact that indoor plants can’t make a measurable difference. But I think their statement overshadows the fact that plants really do have great capacities to clean air.
All plants remove carbon dioxide (CO2) from the air and turn it into oxygen through photosynthesis. This process is probably the most relevant process on our whole planet, as it provides us and all other breathing beings with the oxygen we need to live.
The majority of plants also filter further toxins and pollutants out of the air such as volatile organic components (VOCs) or formaldehyde, benzene, xylene, toluene, carbon monoxide, or particles of fecal matter and mold, and convert them into new plant tissue or release them as harmless by-products.
“Plants can purify the air from pollutants such as carbon dioxide, volatile organic components (VOC), carbonyl, particulate matter, organic compounds, nitrates, sulfates, ammonia, calcium, ozone, and carbonate.”
El-Tanbouly, Hassan and El-Messeiry in Frontiers of Molecular Biosciences (Vol. 8: 2021)
Plants are not only able to filter components out of air, they also filter soil and water and with that, they play a major role as environmental cleaning systems on this planet.
The concept of using plants as environmental filters is known in science as phytoremediation, which means purposefully applying plant filtration to reduce humanmade pollution of the environment. It is certainly one of the promising future technologies as the need for more sustainable and eco-friendly solutions rises.
What Causes Bad Air Quality in Your Home?
You might wonder what the components of air are that we generally think of as “bad” for us. The sources of bad indoor air are many:
- Our breath produces carbon dioxide (CO2)
- Chemical cleaning products residues
- Chemical residues in building materials such as paint
- Moisture issues can cause mold to grow which releases CO2 and allergenic mold spores
- Traffic combustion by-products such as carbon monoxide or particulate matter
- Smoke or fireplace residues
- Industrial residues such as pesticides, chemicals, toxic production by-products
None of these components should be present in high amounts in the air we breathe. Especially in urban or industrial areas, purifying the air in your home is the only solution to not be overexposed to such air pollutants.
Conclusion: Houseplants May Not Significantly Clean Indoor Air, But They Enrich Your Space In Many Ways
Current scientific studies show that the number of plants required to significantly improve indoor air quality is so high that it becomes nigh impossible to have that many plants in a home.
But don’t be fooled by this statement about the importance of plants: Plants do purify air and on a planetary scale, their filtering capacities have a major positive influence on our climate.
Even though houseplants may only make a minor difference in indoor air quality, it is still better to have them than not. There are plenty of other benefits to having houseplants, such as their aesthetic value or decreasing stress levels and making a space feel cosy and alive.
5 Favourite Houseplant Species for Cleaner Air
Overall, there are so many houseplants that are known to clean air that it is difficult to pick one. Some of them are rather undemanding while other plants are quite sensitive and picky when it comes to care and light demands.
As I want this post to be helpful for all of you, I have picked out five plants that will thrive in most households, whether you are a plant beginner or an expert. These plants are also available in most plant stores as they enjoy great popularity.
1. Chinese Money Plant (Pilea Peperomioides) – The Undemanding Eye-Catcher
Pilea peperomioides, also called Chinese money plant or pancake plants, is a wonderful air cleaner and allrounder. I have these plants at home as well as at the office and they just thrive anywhere you put them.
A Swedish missionary called Agnar Espegren first brought the plant to Europe in 1946. Originally, it grows in the Chinese Can Shang Mountains in the Yunnan Province, which explains its name being the Chinese money plant.
It is a low-maintenance plant with lots of benefits:
- Grows incredibly fast
- Filters toxins from the air such as formaldehyde, benzene, toluene, and xylene
- Easy to propagate as it grows offshoots already at early stages
- Thrives even at shadier spots
- Needs watering only once a week (whenever the soil has dried out)
Tip: If you know someone who has a Pilea peperomioides, ask them for an offshoot so you don’t have to buy a new plant. Even tiny offshoots will grow into big plants in no time.
2. Golden Pothos (Epipremnum Aureum) – Fastgrowing Allrounder
Epipremnum aureum or Golden Pothos is also called Devil’s ivy as it is almost impossible to kill and keeps its saturated green colors even when growing in a pretty dark spot. Botanically speaking, it is not an ivy, though.
It has variegated leaves of rich green with golden-yellow stripes or spots. With their long and lush twigs, they can be beautifully draped on a shelf or hung decoratively from a higher place and spread a tropical vibe.
It is a perfect beginner’s plant:
- Grow in indirect light conditions
- Thrives even in shadier spots
- Filters all toxins from the air such as formaldehyde, benzene, toluene, xylene, and carbon monoxide
- Needs watering only every week or two (depending on how much light it gets)
- Easy propagation by growing cuttings in water or soil
This plant grows so fast, you will soon have to cut off some twigs or figure out ways how to drape them around the whole room. Such a stunning addition to your houseplant family!
3. English Ivy (Hedera Helix) – An Outdoor Commons Taken Indoors
Hedera helix, also known as English ivy, Common ivy, and European ivy is the type of ivy you have probably seen many times growing on trees, stone walls in parks, and other public places.
It is also a great indoor plant due to its easy growth and air-cleaning capacities and makes for an elegant hanging plant with its trailing lush vines.
Here’s what an English ivy needs:
- Grows well in bright indirect light
- Filters toxins such as benzene, formaldehyde, xylene, and toluene, and reduces other particles such as fecal matter and mold
- Likes moisture in air and soil (but not soggy)
- Likes cooler temperatures (do not place it near heating)
Ivy you see growing outdoors is tough and relentless, it climbs any surface and can even damage roofs and walls by adhering to them. If you take ivy inside, it becomes much more sensitive as our indoor climates tend to be too dry for it, especially when heating in winter. Make sure to give this plant enough moisture and humidity.
Tip: If you’re looking for a specific variegation of ivy, you’ll find them in plant stores. But if you are fine with the common ivy, you can just take some cuttings from an ivy you find growing outdoors. It’ll work just fine to grow them indoors. Just make sure to choose young, fresh, and healthy-looking vines.
Also, keep in mind that ivy species have poisonous sap that can cause allergic reactions. Make sure to wear gloves when cutting or treating the plant.
4. Spider Plant (Chlorophytum Comosum) – A Purifying Beginner’s Plant
Chlorophytum comosum, also called spider plant, are among the easiest indoor plants to start off with if you are new to plants. Apart from the occasional brow tip, you will have no issues with this plant at all.
Its arching long light green leaves give it a fresh and bushy appearance and feels like having spring in your home all year long.
- Very easy to grow
- Filters carbon monoxide
- Likes bright indirect light
- Likes cooler temperatures
- Need to water every week (dry out in between)
- Easy to propagate
Getting yourself a spider plant will be easy: It is one of the most popular houseplants and you will most likely know someone who already has such a plant – just ask them for one or two of the little spiderette offshoots of the mother plant and pot it in.
5. Weeping Fig (Ficus Benjamina) – Tree-Like Foliage to Enrich Your Space
In their original habitat in Asia and North Australia, Ficus benjamina grows into tall, evergreen trees that are considered sacred to many indigenous groups.
In a pot, fig trees might not become as tall, but they nevertheless grow tree-like and present lush green foliage.
Among its many benefits are:
- Low maintenance once it likes its spot
- Filters toxins such as formaldehyde, toluene, and xylene
- Needs watering only once a week or less (let the soil dry out)
- Can easily be pruned back to have a bushier plant
- Easy propagation by growing stem cuttings in water or soil
Though this last one of my favorite air-filtering plants is also low maintenance, Ficus benjamina can be a bit picky when it is not in a convenient spot.
It doesn’t like too much ventilation around it or changes in humidity. If at the right spot, it will grow steadily without issues. If at the wrong spot, it will let you know like a real drama queen by drastically shedding most of its leaves. Don’t worry, replace it in a more suitable spot and the foliage will regrow in no time.
Please note: Ficus benjamina is of the mulberry family (Moraceae), all of which carry poisonous milky sap (latex). Whenever you are handling or cutting the plant, avoid getting in touch with the sap or wear gloves.