Air Purifying Plants – Do They Work?

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Robert Pavlis

It’s that time of year again, winter is coming. We close the windows and doors of our home to keep out out the cold, and in the process we lock in all kinds of chemical pollutants. Never fear, a few air purifying plants will help with that problem. This must work since all kinds of home magazines, newspapers and web sites tell you it works. Headlines like “the 10 best plants for removing pollutants in your home” appear daily this time of year. How well do plants work at cleaning the air in our home?

Air Purifying Plants
Air Purifying Plants – Do They Work?

Air Purifying Plants Do Remove Some Pollutants

There is no doubt that plants do absorb chemicals and particulate matter from the air. Our outdoor environment is improved by the presence of plants.

It only makes sense that having plants indoors would have the same effect and in fact this is quite true. House plants do remove chemicals from the air in our home. They do remove CO2 and they remove some other pollutants. The real question that needs to be asked is the following:

Do house plants reduce the amount of pollutants in the air inside the home?

These might seem like the same statements but they are not. Plants can and do remove pollutants, but do they remove enough of them to make a difference to the amount of pollutants in  our air? If you had two identical homes and one had a few plants growing and the other did not, would you see a difference in the air quality? That is the important question.

Growing Great Tomaotes, by Robert Pavlis

Air Pollutants in the Home

So what is the big deal? What kind of air pollutants do we have in our home? Why is it suddenly a problem?

Years ago homes in developed countries were quite drafty. Clean air from outside was constantly being blown through our homes, exchanging polluted air with fresh air. Things were good, except that heating bills were very high. Along came the better sealed homes–remember the R-2000 homes? Homes being built today are so much more air tight that they prevent fresh air from coming in.

At the same time, more and more products in the home are man-made and many of these products give off a constant low level of polluting chemicals. The plastic carpet, the fabric on the chairs, and all of our electronics are polluting our air. You might remember formaldehyde insulation? And those air fresheners, scented products and spray cans are some of the worst polluters.

So while our homes have become more air tight, the stuff in our homes are producing more pollutants than ever before. The result is a poor quality of air in our homes, especially in winter.

NASA Tests Plants

In order to better understand this issue, we need to go back in time and see where the scientific evidence started. Some early studies showed that plants absorb VOCs (volatile organic carbons), such as benzene, toluene, octane, and trichloroethylene . This lead NASA to do some research on air purifying plants, which they reported in 1989.  The results showed that in a lab situation, plants did in fact absorb VOCs from the air.

That started an avalanche of recommendations in the popular press. “House plants purify the air in the home”.  People started recommending “the best air purifying plants” for the job. What a relief–buy a few house plants and we are all saved from air pollution.

Microbe Science for Gardeners Book, by Robert Pavlis

By now I am sure you have guessed that this is all a myth.

The Birth of a Myth

Before looking at the reality of the situation it is educational to understand how it all went wrong. This myth was born, like many others, as a result of two main mistakes.

  1. Results obtained in a controlled lab situation were extrapolated to a field environment–our homes.
  2. Actual data was exaggerated and misinterpreted by the media.


Both of these mistakes happen all the time with almost all topics, and they happen a lot with gardening advice.

The early testing done on plants used small lab chambers, that were highly controlled, and which were crammed full of plants. They did not simulate the situation in our homes and the researchers doing the work never claimed their work showed house plants would reduce pollution in our homes.

The media took the results, selected the numbers they liked best, jumped to unfounded conclusions and announced “air purifying plants work to clean our air”.

To have a closer look at the details of these mistakes have a look at A Myth is Born – Plants Don’t Purify Air.

Plants Don’t Improve Our Indoor Air

More recently a few researchers have studied the effect of plants in real world situations. These studies were done in offices, but this is fairly similar to our homes.

These studies show that the level of pollutants do NOT go down over time.

Why is there such a difference in the studies? The main reason for the difference was that the initial lab work was done with a lot of plants in a small space. To establish this in our homes we would have to have a 100 house plants in every room. That’s not practical–it would be great to have all these plants–but not practical. Having a plant or two for each room in your home will just not make much of a difference.

The second reason for the difference is that in our homes the material in them is constantly giving off pollutants. These are produced faster than plants can remove them. In the lab test chambers, the pollutants were injected once and then the air was monitored to see a reduction in pollutants. These are two very different situations.

Here is what the EPA has to say on their FAQ page (ref #2): “The only available study of the use of plants to control indoor air pollutants in an actual building could not determine any benefit from the use of plants“.

Best Plants for Reducing Pollutants

You will find lots of lists recommending the best plants for removing home pollutants. I am not sure where this information comes from. Most of the studies show that there is little difference between one plant and another. The size of plant and the number of plants is more important than the variety.

Plants vs Microbes

If plants removed pollutants from the air, then more leaves should remove more pollutants. In one study NASA measured the ability of certain plants to remove pollutants–this gave them a base line value. They then removed some leaves. It seems pretty obvious that if you remove leaves, the plant will remove less pollutants–right? Wrong. What they found was that removing leaves improved the plants ability to remove pollutants.

Long story short, and after many more tests, they were able to show that it was the microbes in the soil that were removing most of the pollutants. The microbes were much more efficient at removing pollutants than the plants–surprise!

It seems quite obvious to me that if we went back to dirt floors we would solve our home pollution problem, but the popular press has not picked up on this idea!

Air Purifying Plants Will NOT Clean Your Air

House plants are a great addition to your home, but they have no real effect on the quality of your air, unless you have hundreds of them. The microbes in the soil are more valuable than the plants as far as cleaning air goes, but even they have little effect on the quality of your air.

The best thing you can do is to allow fresh air into your home, and reduce the number of cleaners, and perfumed products you use. Fewer renovations, and fewer electronic devices will also help. Stop using products sold in spray cans.

Kamal Meattle – Plants and Air Purification

Kamal Meattle presented a very convincing TED Talk video on line promoting the idea that plants purify air. You can see the video and read the full story at, Kamal Meattle – Plants and Air Purification.

New Study on Office Buildings

A new field study has been brought to my attention and is reviewed here. The study is called The Potted-plant Microcosm Substantially Reduces Indoor Air VOC pollution: I. Office Field Study by Ronald A. Wood et al.

This study was done using three buildings at the University of Technology, Sydney, Australia. Zero, 3 or 6 plants were put into various small offices and total VOCs were monitored over time. There was no reduction of VOCs in any of the buildings as a whole. Building 1 was an administrative office building and there was no reduction of VOCs in the offices with plants. Building 2 and 3 were mixed use offices containing both offices and laboratories. Some reduction of VOCs occurred inside the offices with plants but not in the building at large. There was no difference between using 3 or 6 plants and the reduction was only seen when the offices had high levels (>100 ppb) of VOCs present. These high levels are above that found in a normal home.

In conclusion, the study indicates that adding such plants would have a limited effect, if any, in a home with average VOC levels.

A more detailed analysis can be found in the discussion section of A Garden Myth is Born – Plants Don’t Purify Air.

New Metadata Study

A new metadata study has reviewed all past studies and compared the plants efficiency to standard air exchange rates. What they found is that plants don’t reduction VOC levels in a home.

Our homes are quite leaky, and air is constantly flowing into our homes from outside. This reduces VOC levels far more effectively than plants.

Do Houseplants Increase Oxygen Levels in the Home?

Several people commented on my posts that houseplants were still valuable in the home because they increase oxygen levels and that makes us feel better.

I have now looked into this claim in Do Houseplants Increase Oxygen Levels?


1) How Well do Air Plants Perform as Indoor Air Cleaners?:

2) Indoor Air Pollution:

3) Photo Source: Spaceo


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Robert Pavlis

I have been gardening my whole life and have a science background. Besides writing and speaking about gardening, I own and operate a 6 acre private garden called Aspen Grove Gardens which now has over 3,000 perennials, grasses, shrubs and trees. Yes--I am a plantaholic!

24 thoughts on “Air Purifying Plants – Do They Work?”

  1. I’m not sure if I follow what you can’t find, there were multiple studies referenced in the link I provided above. You seem to discount any information that isn’t directly taken from the field, but there are multiple sources that did studies in real office spaces. Here is an example of one from the previous link that I quoted from above, “Purification Capabilities of Golden Pothos and Peace Lily for Indoor Air Pollutants and Its Application to a Relaxation Space”,
    Takashi OYABU, Ayako SAWADA, Hiroyuki KURODA, Tomoaki HASHIMOTO, Takayuki YOSHIOKA.

    Based on their materials and methodology it looks like they were not using the forced air carbon filter pots either, just relying on the plants and the soil bio-microcosm.

    To quote the abstract, “Plants were also set in a real environment. Total Volatile OIganic Compounds (TVOC) and odor grades were
    measured to examine purification effect of plants. Removal rate for TVOC was 74% and that of odor was 68%.
    It was confirmed that plants had high purification capability for bot of VOCs and odor even in the real environment.”

    They got some “useless” information gathered from plants in test containers as well as from a real common room in an office building. They have the plant layout and office room dimensions included.

    Part of your argument against the efficacy of house plants at cleaning air seems to hinge on denying the existence of sick building syndrome. Buildings exist with poor ventilation where levels of these VOC’s build because they are more similar to the Biodome than a well ventilated home in regards to “fresh air”.

    Several more studies from Australia on the subject can be found here, I am happy to pass along more specific studies if you would like them.

    I love most of your work and am happy to help find additional studies if none of these are sufficient enough to meet your burden of evidence. You seem to discount Wolverton’s life work; he has done more follow up studies since his original NASA experiment. Particularly on his website he has some simple charts comparing the average concentration of air pollutants in typical hospital and office spaces to the removal capacity shown in the peer reviewed experiments you consider invalid, which has always been compelling to me.

    • If you look at the study you linked to and my blog post, you will see the problem.

      From your study s.Thedimensionwas575×510×1000

      Any experiment in a small chamber with a single injection does not give mimic a room. A room is large in relation to the plant, and it is continually injecting pollutants.

      I never said plants don’t remove chemicals in a small chamber. I said they don’t purify the air in your home.

      • I don’t think you read the experiment, specifically section 3.4 “Application in a real office environment”: 3.4 Application to a real office environment”
        “The purification effect of plants was examined by installing the various kinds of pot plants in a healing space. The space was partitioned in a commercial building. The space was also the places of recreation
        and relaxation for the citizens. The layout is indicated
        in Fig.8. ”

        They have a layout in a real room that they tested, as do other studies. I would be happy to supply more if you are interested, I would specifically point you towards the Australian studies by Burchett and Torpy. Specifically here is a field study of an office building:

        This experiment is a field study of offices. Please note it does both “useless” chamber studies to confirm the findings as well as field studies in the offices.

        • You are right – I did miss the second part.

          1) They measured base values for 2 days, then added plants and measured for another 2 days. That is not nearly enough to get good data.
          2) The drop was 75%, when other similar studies showed no drop.
          3) There is no detail about the room, how it was used during the 2 days, the kind of ventilation etc.
          4) The most significant missing piece is that they did not remove the plants after the two days and record another baseline.
          5) No stats are reported with the data.

          Australia Study:
          1) Data for individual offices is lacking. Instead they clump whole buildings together and in a few tables more than one building.
          2) Fig 1, no effect from plants, Fig 3 shows plants reduced VOC, Fig 4 shows plants increased VOC, Fig 5 shows plants increased VOC – I see no explanation why this is the case.
          3) For some reason they picked 100 ppb as a cut off level and recalculated the data. After doing this, the data shows plants remove VOC, but I see no explanation as to why 100 was selected. It seems a round number that made the data come out to way they wanted it. What are the typical levels in a home?
          4) From P 10: “Figures 2a and 3a show TVOC levels for all 18 weeks for each building, where there were no significant differences between the two buildings in reference-office TVOC levels, nor between reference and planted offices in either building”
          5) From P 11: “In each building, with the combined results for all weeks sampled (Figures 4a and 5) no significant difference in TVOC levels were distiguished between reference andplanted offices, although recorded levels in planted offices were slightly higher than in unplanted offices. “, which acknowledges the fact that in some cases plants increased VOC.

          (10) (PDF) The Potted-Plant Microcosm Substantially Reduces Indoor Air VOC Pollution: I. Office Field-Study. Available from: [accessed Apr 05 2021].

          They are acknowledging that fact that when the data is grouped in this way, there is no effect by plants.

          There is also this statements:

          “from the current study it would appearthat VOCs in the gaseous phase in contact with the potted-plant microcosm can bedegraded by substrate microorganisms via the same metabolic pathways as those involved in the bioremediation of oil spills or the degradation of other soil-bornearomatic hydrocarbons (by partitioning into adsorbed water on the potting mix particles, and thus become available to the microorganisms). ”

          There is nothing in this study to even remotely suggest such a conclusion.

          This work was not well presented, important data is missing, and key explanations are missing. In some cases plants either did not reduce VOC or they even increased it.

  2. I think this was biased as you referenced a small office with a couple of plants to a home. I live in a small one bedroom apartment and with my 20 plants crammed along my patio doors, I would suggest that I wouldn’t need a hundred plants to improve my air quality, the air quality here was tested and is much better after 6 months after these plants settled.There are far too many variables and as much as a single plant not improving air quality, to which I agree as it’s ridiculous to think otherwise, I don’t think your statement that you would need a hundred plants to improve air quality or debunk the myth is any more valid. If you did a scientific experiment per size of home and style and this how many or how big the pland would need to be, this would then be more believable.

    • My suggestions are not numbers pulled from the air. They are based on the testing that has been done.

      More testing would be great – but I can only report on what has been tested.

  3. I knew plants were overrated. Close your windows and the radon will kill you. Open them and the gross exhaust-filled air makes breathing unpleasant. If you don’t like it, you can either move to the country or run energy-hungry air-scrubbing appliances.

  4. This will be out of the subject matter ever so slightly,
    Do you have any thoughts on what effect a large garden would do for the outside air?
    For example, the ability of a large garden in ones personal yard space to lower carbon emissions within an effective parameter. Effective being a viable impact that if replicated on a larger scale, could increase the underlying benefits to immediate air quality over a yet to be determined amount of space, over a yet to be determind amount of time.
    I’m actually researching this currently, which led me here.

    Also, nice investigative work here. I enjoyed the insight thoroughly.

    • On the surface it would appear that plants reduced the VOC, but…

      1) There is no information about the rooms. Were they open, or closed? No information about the building.
      2) They selected the plants because they are “well-known to remove most indoor harmful gases” – so the researchers were very biased – there is no such evidence.
      3) There is no information as to how often measurements were taken, or for what time frame?
      4) How was the control room selected? How does it differ from the others? No information.
      5) The data is not marked to show which values are statistically significant. They do say ” the concentration of all substances in the case group applied with the plants and control group was observed to decrease, but there was no statistical significance in the control group. However, there was a statistically significant decrease in all substances except benzene.” Not clear what this means, and I don’t see the data supporting it.
      6) For PM they used “adaptation period was set for about two months”. Was this also used for VOC? No idea. What is an “adaptation period”?
      7) One of the results for Benzene is “34.50±106.94”. A reading where the error is 3 times the value is suspect.
      8) no information on how any of the VOCs were measured.
      9) What was the natural ventilation like?
      10) These were two new facilities. You can expect new facilities to have higher values, that drop off after a settling period – eg paint dries. There did not measure the same rooms after removing the plants. In fact we don’t know if the measurements with plants was done before or after empty rooms.

      The write up for this work is very poor. Many publications would not accept such work for publication.

  5. I agree with most of the points raised in this article and there certainly is a lot of exaggerations out there. The statements about Wolverton are correct and the prior EPA study points to the correct conclusions. Namely, the Wolverton studies did not take into account volumetric differences i.e. how a plants removal ability would be diluted in a much larger ‘room’ environment as compared to a small chamber.

    The subsequent book written by Wolverton is frankly non-scientific garbage, a farcical rating system has been created on a number of plants which do not link back to his scientific work at all – a money making exercise, I am sure. Which has created a lot of these ‘myths’ in the first place that researchers like myself are trying to row back from.

    I unfortunately feel this article is too far the other way, other than Wolverton you have quoted ‘one’ office study by Wood et al. there are at least 100 now. The fact that you claim it a ‘myth’ off such little evidence is rather hypocritical of your own article and you are again spreading a ‘myth’ but in the other direction. Yes, some of the studies show an unrealistic number of plants are required, but some are much more realistic especially with the ever increasing prevalence of green walls.

    As for research, it has to occur in simulated ‘chamber’ conditions first, whilst an understanding of techniques and the technology is gathered. At the moment the complexity of having > 200 indoor pollutants all removed in different ways/amounts by each houseplant under different environmental conditions is quite challenging. Most of the pollutants indoors have not yet been tested, also how many houseplants are available worldwide? There is clearly a lot of research left to do. Mixtures of pollutants also change how plants react, this as of yet has barely been tested and adds another level of complexity. Everyone is wondering why the results are not encouraging? We have barely scratched the surface of this and although this article is more sensible that most it is again, not helping,

    • My article did not “look at one building study”. I looked at several, and reference #2 additional studies.

      You claim that there are now 100 building studies, and yet you did not give a single one? Please respond with a couple that show plants do work in buildings and I will happily review them.

  6. Thanks for the good read and being a voice of reason.

    I don’t think most people understand that the microbes living on and around the roots are a major part of the bioconversion of micronutrients into useful plant food, and most of those micronutrients would be toxic wastes to you and I.

    It is that series of symbiotic relationships that process soil nutrients (human toxins) into complimentary growth for each successive microbe and eventually the plant itself. Nearly all of those toxins are either broken down into less toxic forms to be consumed by another, used for energy and growth for each one in their own time.

    Trace amounts of some toxins will be absorbed into the plants virtually unchanged, but locked safely away by the plant itself within its cell walls… Until the leaves eventually drop off and begin to decay. Once that happens, the toxins that remain will be released back into the atmosphere from whence they came and the cycle begins again.

  7. Love this article! A lot less bullshit than what I’d expect from an average blog post.

    Curious to what your actual solution would be?

    As for myself:

    Some of these air purifiers, they are rather expensive and I will not write the brand here seemingly do the trick of actually removing VOCs. What is your verdict on them?

    • This is not your average blog 🙂

      I have not looked into air cleaners, but there is no reason that they would not work to some extent – the question is do they remove VOC’s faster than they are produced?

  8. Since you at least read the research papers on VOC removal (which is actually remediation), you made the correct statement by saying that it is the microbes that do this. The original data wasn’t exaggerated, it was just performed in optimal conditions for a very short period of time. Chemical remediation happens in all areas of the plant (for which there are specific names for each area), but the root zone is where the majority of where it happens. But you you forgot to mention that these microbes can’t survive without the plants…

    All plants have relationships with microbes that make local nutrients available to the plants in exchange for food (sugars) from the plant.

    While the media may be portraying this information in a different way, they’re not completely wrong. Air purifying plants WILL clean your air, because they create the microbial communities to do so. Do you expect the media to tell people “use dirt to clean your air” ?

    I have personally performed these tests in isolated chambers with formaldehyde, benzene, and xylene. I have seen the chemical levels diminish, and the plant survive. You haven’t debunked anything, you have just provided the correct context for what’s actually going on.

    • It is true that without the plants you would probably not have as many microbes in the soil. But there are two main points to my argument that plants do not purify the air. One was that it was the plants. The second point, which is the main one, is that the amount of plants needed to have any impact on a room is far more than what anyone would use.

      The media and all those thousands of click bait sites claim plants clean the air in your hone. They don’t. The air remains the same with or without a few plants.

      In order for anyone to make that statement they would need to show this in a study. The study would analyze VOC levels in a typical room, not in a chamber. There have only been a couple such studies and they do not show a reduction of VOC in the rooms. Since you seem to be involved in this kind of research, let me know if you find such studies.

      The original data was exaggerated, not by the scientist, but by the media. They selected the single highest value in the study and used that for reporting the effectiveness of plants. The media also reached conclusions that the original NASA study never reached – another form of exaggeration.

  9. Our living/plant room might say a different story 🙂 – just a joke.
    True that one has to have lots of plants in a room for a real effect, but can you please, place this myth on top of the ‘good’ ones for all the other benefits the house plants bring?

      • If you had 100 in each room you undoubtedly have the ability to reduce VOC’s in your house and yet you still call it a myth? I agree with other commenters, you are spreading a myth in the other direction. Nasa’s research showed that even if you have plant’s in the room, it isn’t just the soil that contributes to VOC reduction. It is the symbiotic relationship between plants and soil microorganisms that reduce VOC’s.

        Directly from the NASA article from 1989, the results and discussion section: “Early tests demonstrated that potting soil, after all foliage had been removed, was more
        effective in removing benzene than pots containing full foliage and soil. However, further
        studies and careful observation determined that this phenomenon occurred only when large
        amounts of foliage covered the potting soil surface, reducing contact between the soil and
        the air inside the chamber.”

        Also, nowhere in the materials and methods portion could I find the “initial lab work was done with a lot of plants in a small space” detail that you mentioned. Also, I did find that NASA used two different size chambers, so there was an attempt at increasing volume to test VOC absorption correlations.

        It seems that in your attempt to say others glossed over important details, you’ve glossed over them yourself. For example, whether or not your comment about reverting back to dirt floors would be beneficial to us or not was a joke, it was still misinformative as it implicates that it is the microbes that are the effective ones and not the microbes, when the NASA testing even attempted to control (and adjust their results) for the amount of pollutants absorbed by the microbes.

        Instead of referencing other generalized information such as the EPA’s FAQ’s, please read the actual scientific articles. There is an astounding amount of important details within them, and calling something a myth of out looking at every single detail is premature. There haven’t been studies looking at plants affects on house air quality in the home of a smoker, how plants can reduce VOC’s in close proximity to cooking appliances or in garages where people store cars. There is a ridiculous amount of work to be done still, and claiming that plants improving home air quality is a myth is just (or worse as it discourages important future research) unhelpful.

        • The 100 plants is purely an estimate. No one has actually tested that number of plants in a home. Nor is it reasonable to have this many plants in each room of the house – they do need light. If you place them near the window – how does that affect the movement of VOCs from the other side of the room?

          No evidence this will work, and it is not a realistic situation.

          re: “It is the symbiotic relationship between plants and soil microorganisms that reduce VOC’s.” There is nothing in the NASA study to suggest this. Plants grown hydroponically will also remove VOC and microbes in soil do not need plants to carry out their biochemistry.

          re: “please read the actual scientific articles” – that is precisely where I got the information.

          If you have new information to support the idea that plants will clean the air in a home – present it so we can discuss it.

          • I definitely think the benefits are misstated, but I do think the potential is out there and more studies are necessary. Both biosphere 2 and Biohome studies have corroborated the findings from the original NASA study and expanded their potential. In the biohome they juiced up the VOC concentrations and demonstrated lady palms increased their absorption of formaldehyde the more they were exposed to. This is a recent report that goes over some of the extended studies beyond the original NASA study:

            Stated bluntly from their conclusions, ” Extensive studies by WES as well as other scientists in Europe, Canada, India, Korea, Australia and Japan have provided scientific evidence that interior plants can help improve the air quality within energy-efficient buildings”.

            Anecdotally, I have about 150-200 cubic feet of “plant” in about 300 square feet of room, and if nothing else they help catch a lot of dust floating around and I think growing my interior jungle has helped some of my allergies, but I have zero evidence on hand for that claim. The Biohome had enough plants in it that they were able to be used as the source of oxygen in a sealed building, and those are numbers of plants I think you need to approach to hit any noticeable difference.

            Will putting a phal on your window sill improve your air quality and help you sleep better? Absolutely not. Is there potential for live plants to be incorporated into our buildingscapes to improve indoor air quality? It is looking promising.

          • ” Extensive studies by WES as well as other scientists in Europe, Canada, India, Korea, Australia and Japan have provided scientific evidence that interior plants can help improve the air quality within energy-efficient buildings”.

            If this is true, why can’t I or any other researchers in this field find any??

            Biodomes are not homes.

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