Kamal Meattle – Plants and Air Purification

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Robert Pavlis

In 2014 I wrote a post called A Garden Myth is Born – Plants Don’t Purify Air, which has become one of my most popular posts. A recent comment on that post about a video by Mr. Kamal Meattle has prompted me to write today about another story related to plants purifying air.

Mr. Kamal Meattle has become well known for a short TED Talk video where he talks about converting an office building in New Delhi, into the cleanest building in India. His secret is the use of air purifying plants.

Plants cleaning the air in an office, desk designed by Julio Radesca
Plants cleaning the air in an office, desk designed by Julio Radesca

The Kamal Meattle TED Video

The place to start is with the video which is quoted and discussed in hundreds of places on the internet as proof of the fact that plants purify air. It has been watched by almost 3 million people.

What does the video imply?

  • Plants purify the air by remove formaldehyde and VOCs (volatile organic compounds).
  • Plants produce fresh air.
  • Plants have reduced the incidence of several medical issues by improving the quality of air.
  • Government of India has published a study verifying these facts.

I use the word ‘imply’ here since the video tends to give you a different impression the first time you watch it, than when it is watched and listened to with care.

Soil Science for Gardeners book by Robert Pavlis

What does the video actually say?

  • No data is presented to show that plants reduce the level of formaldehyde or VOCs.
  • No data is presented to show that oxygen levels have gone up.
  • 1,200 plants were used in a 50,000 sq ft building that housed 300 occupants.
  • The only study mentioned was done by the India government – no data from it was presented.
  • The term ‘fresh air’ is never defined.

In fairness to Mr. Kamal Meattle this was a mini TED presentation with limited time available, but it is surprising that there is no data presented to support the ideas presented.


If the above video does not run try this link; http://www.ted.com/talks/kamal_meattle_on_how_to_grow_your_own_fresh_air#t-224937

Some Back Ground Information About Mr. Kamal Meattle

Mr. Kamal Meattle is the CEO and director of Paharpur Business Center, a company that rents out clean air office space to other companies. Kamal has been active in trying to reduce pollution problems in India and continues to look for new technologies that can be used to solve air quality problems.

Mr. Meattle has received several awards for creating and maintaining a building that meets high air quality standards.

National Geographic reports that “Since January 2013, Meattle’s company has created plant-based air-filtering systems for more than 700 homes in India’s capital. It’s also working to clean the air inside the embassy schools of the United States and Germany”. It is clear that his company is in the business of selling clean air solutions.

Changes Made to the Building

If we return for a moment to the video and try to understand what was done to the building to improve air quality it seems fairly simple. Add 1,200 plants of waist or shoulder height to the building which has 50,000 sq ft. That is a lot of plants, but it is also a big building. It works out to a plant for every 41 sq ft, or one plant per 10′ x 4′ area.

An average home of say 1,500 sq ft would need 37 plants to have an equivalent set up.

The problem with the video is that it does not tell the whole story.

It turns out that many of the plants are located in a greenhouse situated on the roof of the building. The incoming air flows through this greenhouse before entering the building. I think it is reasonable to assume that plants sitting in a sunny greenhouse will have higher metabolism and therefore be much more effective at cleaning air than the same plants sitting in the dark corner of a home. Even a sunny window can’t match the sun provided by a roof top greenhouse.

The real problem however is that the building was also outfitted with a sophisticated air cleaning system for removing chemicals from the air. The incoming air is cleaned by this system before it goes through the greenhouse. The building has both an air cleaning system and plants.

Why was this significant point not mentioned in the video?

The Study by the India Government

I was not able to find the study that looked at the effect on plants on the air quality in the building in question. I checked the Paharpur Business Center website to see what evidence they might have to support their claims – none was found. I then contacted Mr. Meattle and he was very kind in replying promptly. He forwarded a copy of the study to me.

A summary of the report can be found on the PBC web site and the full report can be downloaded from there.

The study does not make any comment about the plants ability to remove pollutants from the air. In fact it does not mention plants. It was never the intent of the study to look at this aspect. Instead the study looked at health issues inside the building and compared them to the general Delhi population.

The study referenced in the video has nothing to do with plants.

Where is the Data?

I had asked Mr. Meattle for information showing that the plants reduced the chemicals in the air. He replied with “There have been many studies done over the years. We are not a research institution and hence these were done for our own interest.” But his company is in the business of selling plant air cleaning systems. One would expect at least some internal data to support their claims.

He did send me a picture of their current air quality, but it shows that both inside the building and outside the building have total VOC levels of 0 ppb. The zero value for Dehli is not correct. I’ll give them the benefit of doubt and assume the VOC’s were not being monitored.

There seems to be no data to show that the plants are removing chemicals from the air.


I want to be very clear about what we know and don’t know.

I have no doubt that the building in question has supplier air. I also believe the Mr. Meattle has done a good job of finding ways to clean the air in his building and that he firmly believes that plants play a big role.

The plants do remove CO2 and add O2 to the air. Although this is good for human health, it is not the question being asked here. This post is all about removing organic chemicals like benzene and formaldehyde.

The building was set up in 2008, the TED video is dated 2009 and it is now 2016. In that time it would have been quite easy to test the level of organics in the building, with and without plants. If done through a university the results could be published in a peer reviewed journal.

One is left wondering why such a simple test was not done?

The National Geographic reported that John Girman, former senior science adviser at the U.S. Environmental Protection Agency’s Indoor Air Division, said “a 1,500-square-foot house would need 680 plants to duplicate NASA-like benefits, and the result would be an indoor jungle” .  Interestingly, in my previous report on the NASA study I figured that a 1,500 sq ft home would need 350 large plants or 750 small plants.

The work by Mr Meattle is interesting and worthwhile, but the currently available data does not support the idea that plants clean the air.

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. Can Houseplants Really Clean the World’s Smoggiest City? http://news.nationalgeographic.com/news/energy/2014/12/141230-can-plants-really-clean-indias-air/
  2. Photo source, used by permission; Julio Radesca

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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!

14 thoughts on “Kamal Meattle – Plants and Air Purification”

  1. this is all very interesting! greate work! I have wondered about the nasa study a lot, as it is allways taken as proof for many things in strange ways, tried to find out whether actually all the plants tested are simply now seen as air purifyer, and if an<one has ever tested which plants are actually best, which soil, with which microbes and fungi, and which way of air getting streamed through the soil.. this is the best information I have so far found 🙂 someone who is not just trying to sell something..

    I am truely deeply interested in what realy works. my guess would be something like terra preta, which is a soil high in coal, could be actuvated charcoal, and something like vermiponics, using the bacteria and manure produced by worms as fertilizer, and actually as kind of a probiotic, perhaps in combination with some micorizal fungy, and an air stream through or along the roots..

  2. The TED talk by Kamal Meattle started me on this journey to research the effectiveness of houseplants on indoor air quality. Almost all of the articles I looked at online about this either made outlandish claims that was not backed up by any data and therefore could not possibly be true, or they made more reasonable claims that sited the NASA study and therefore seemed true. But, none of the reasonable articles (except for yours, https://www.gardenmyths.com/garden-myth-born-plants-dont-purify-air/) mentioned how the NASA study used carbon filters that concentrated on the root system to do the work, which none of us do with our indoor plants. This effectively makes the NASA study irrelevant to practical indoor usage and its odd that no one else is aware of this.

    However, I did come across this article (https://www.livescience.com/38445-indoor-plants-clean-air.html) from Live Science that mentions 2 other studies from Pennsylvania State University, the University of Georgia. I also find it odd that almost no other articles mention these 2 additional studies. I took me a while to hunt them down but I found the actual published studies.

    Pennsylvania State University

    University of Georgia

    The Pennsylvania State University study concentrated on the foliage of the leaves to do the work by covering the top of the pots, eliminating the usage of the roots to do the work. They studied 3 houseplants — the snake plant, spider plant, and golden pothos and found that they did make some significant difference in reducing the amount of ozone in a simulated indoor environment. It also seems like the time of day doesn’t seem to affect the effectiveness of the plants, which seems odd to me since plants should not be able to photosynthesize at night. However, this study did seem to have some more practical implications than the NASA study, since it utilized the plants in a manner that more closely resembles “real life.”

    The University of Georgia study also had some promising results on reducing other VOCs using common house plants in a practical setting.

    But, overall I think that ultimately to have the houseplants make a considerable difference in your household you probably have to have an impractical amount of plants and and light or live in a green house.

    • Thanks for posting the links:

      The NASA study did look at special carbon filtering pots, but the first part of the experiment used standard pots.

      First study:

      Why use a simulated chamber instead of a real home? How close is the simulated chamber to a home? It might be a good way to do an initial study, but now you need to use a real home.

      Ozone probably reacts easily once inside plant leaves. It is quite possible they remove ozone – but this is not usually considered a pollutant in the home.

      Second study:

      This is really a repeat of the original NASA study, without the use of carbon filtering pots. The data can’t be extrapolated to a home situation.

      I contacted the authors of this study to see if they tried to do some extrapolation calculations to see how many plants a home would need to have an effect of VOCs.

  3. Does having the plants listed in the NASA report in the bedroom have any positive advantage apart from the mere esthetic one? On the many websites you can read how they regulate the himidity, ionize the air (which I dont even know the meaning) and emit tons of oxygen at night, on top of cleaning the air. Is any of this scientifically proven? txs! Gobb

    • I have written, but not posted yet, on plants adding oxygen to the air. They add virtually nothing compared to the amount we consume.

      They may regulate humidity a bit. The benefits of ionization of the air is pseudoscience.

  4. I have seen this Ted Talk and it motivated me to research some of these plants and drop a line in several house plant forums in order to see which plants would best help me oxygenate my basement apartment but you’re essentially saying it’s an entirely hopeless endeavor devoid of merit? If not then do you have any suggestions, research regarding plants and oxygenation of indoor spaces, and any other information I might find helpful?

    • My next post will be about the oxygen produced by plants. In short, the amount they produce is insignificant compared to the amount we consume.

  5. “The VOCs do not build up over time” WOW really? WRONG! More correctly they are ventilated frm our homes every time a door or window are opened. That is why many products warn to use ventilation to use them. the VOC’s they emit are strong and can be dangerous. Also I am surprised that you did not mention that plants themselves are the highest producers of VOC’s, generally speaking. I feel as if you have done the same type of generalization in this and your previous piece that you are suggesting the people did with the NASA study. Do plants improve air quality in and out of buildings ABSOLUTELY! Can they clean specific VOC’s from chemicals? Possibly. I concur that the study was poorly done and the media attention even more poorly researched. I do not agree that the theory is without merit. I believe that a far better multitude of studies would be needed to determine that, either way. I think such studies would be a waste of time and money. I think that we can all agree that plants CAN make for a better environment without knowing exactly what they and cannot remove from the air and even less important which plants remove what particles. I think an article outlining the various plants effects on allergies and animals and children would be far more beneficial. I think a lot of things that probably do not matter to others any more than this should.
    THAT is what I think.

    • You said that VOC’s are “ventilated frm our homes every time a door or window are opened”. Correct. That is one reason why they don’t build up.

      Re: “Also I am surprised that you did not mention that plants themselves are the highest producers of VOC’s”. Where is the reference to support this? Secondly, this was not the topic of this discussion – that is why it was not mentioned.

      • They way that you put it made it sound as if they do not accumulate, ever, but they DO…. The correct statement would have been
        “While they do buildup and can accumulate, they are ventilated from crevices, gaps, doors, windows and other places that the air is allowed to escape our homes.”

        As to VOC’s being from vegetation…
        REALLY? If you know ANYTHING about what a VOC Is and how it is produced then a resource that the plants are the largest producers of VOC’s, ( and is the cause of the odors we smell), it is well established but ok want a source?
        While I understand this is not a sturdy resource, it is where I started to confirm my information:
        The majority of VOCs are produced by plants, the main compound being isoprene. The remainder are produced by animals, microbes, and fungi, such as molds.

        Natural emissions are responsible for a major portion of the compounds, including non-methane volatile organic compounds (NMVOC), carbon monoxide (CO) and nitric oxide (NO), that determine tropospheric oxidant concentrations
        Vegetation is predicted to contribute about 98% of the total annual natural NMVOC emission.

        The largest source, by far, is natural emission from vegetation.

        Do I need further sources?

  6. So then by your own admission, YES, plants clean the air. no one is claiming their plants clean up to 90% of the air within 24 hours as in the NASA experiment, simply they are stating that YES they clean the air. if you had 10-20% of the number of plants you and the EPA state are necessary to replicate exactly the results then you would be getting 10-20% the benefits of the clean air effect. and if that 10-20 percent represented by 35-70 large plants or 68-150 small plants outweighed the new introduction of more pollutants than you have a NET positive effect on your indoor air quality that would increasingly get better with each passing second. But even if you didn’t have 35-70 plants and only a few the net effect is plants clean the air, even if only by a fraction of a percent to a few percentage points. Meaning having plants are beneficial not only in your mood and general well being but they would clean the air as mother nature has designed them to do.

    • You are missing the main point of the posts. Yes, potted plants remove VOCs. But as fast as they remove the VOC, the man-made material in the room replaces it. So the level of VOCs in the room never goes down. The air never gets cleaner.

      The amount of VOCs in the room remains the same with or without plants.

      • No, I don’t believe I have missed the point… these VOCs will always be reintroduced into the home, however without plants “soaking” up some of these pollutants then they would just keep adding up and up and up but with plants you can reach an equilibrium where instead of compounding VOCs hour after hour the plants actually help to either slow down the compounding effects or possibly stop them from increasing in volume when measured in PPM (in the case where you have so many plants sufficient to accomplish that task)

        The point should be your home is healthier with plants then without, more plants = less VOC accumulation and therefor healthier indoor environment. Which means YES< plants purify your air, never assume they make your home 100% sanitized but plants = better air quality just like carbon water filters = better quality water, neither is perfect and neither do the job 100% but if you don't have plants filtering the air then your lungs become the only filter for the air you breath. (I'd recommend medical grade hepa filtration system plus plants especially if you suffer from a lung disease)

        in summary: Plants = better air and some filtration is better then no filtration where your lungs would absorb all the pollutants. So show your lungs some love and buy some plants and a hepa filtration unit.

        • If you were correct, the levels in our home without plants would build up to huge levels until it would be too toxic for us to live in the home. That does not happen. The VOCs do not build up over time. They reach an equilibrium point with or without plants.

          There is no evidence that plants make the air in our home healthier.


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