Quote from Michael on November 18, 2019, 2:02 pm

House do plants clean the air

Yep, houseplants DO clean the air. It's that simple. Perhaps, you've read some contradicting information recently.  You might have read something in National Geographic, or CNN, or TIME or New Scientist, or any one of somewhere in the neighborhood of 30,000 citations that have popped up since November 6th  2019. What changed? Actually, nothing.

Is the idea that houseplants do clean the air controversial and why is everyone talking about it?

No it's not really controversial.  We've mentioned the air cleaning benefits of plants before. For a long time the common wisdom is that plants change carbon dioxide and light into oxygen which cleans the air. In September of 1989, NASA published a study showing how, in closed spaces (like a space station) plants might be useful to not only convert carbon dioxide into oxygen, but also clean the air of chemicals. This is was important to NASA. In a sealed environment like the International Space Station man made materials can release chemicals into the air (think of that new car or new couch smell) that require specialized filters to clear. In the study they published which plants were better at cleaning which kinds of chemicals and at what rate in a sealed environment.

A new study on the air cleaning power of plants was published on November 6 2019 in the Journal of Exposure Science & Environmental Epidemiology. This article argues that in open environments, on Earth, with our current atmosphere, opening windows and using HEPA filters on your HVAC system clean the air faster than houseplants do... duh!

Of course they don't exchanging the air in your home or office, faster than a plant can absorb it will OBVIOUSLY clear the air faster than plants could do on their own.

It really seems like someone copied someone's homework and changed the work a little...

Figuring out how well plants clean the air makes for funny reading material

Take with a grain of salt that these are scientific journals we're talking about and not a TIFU post on reddit. There's a lot of information and usually years of work put in to creating these types of publications. Which brings me to part of my point of this (and ~98% of all the blog and news and e-zine) articles about the original articles. They (including this article) are summaries, with lots of opinion, based on information the authors (including me) don't 100% understand attempting to educate you about something that we thought you'd think was interesting. The next step should be where you go read the cited articles... I really hope you do.

What's interesting here is the math. Without getting too deep into it, the main part of the issue is that plants are very slow to exchange air. As an example most bathroom vent fans move 50 - 100 times more air per hour than a typical house plant. Adding more plants increases their effect. Imagine how great your house would look with hundreds of leafbabies.

At the end of the day, the new information in the November 2019 study does not invalidate the 1989 NASA study, but sort of finishes it. NASA went into depth about how well each type of plant did in cleaning up harmful chemicals in a sealed environment over a 24 hour period. The latest study went into depth about how fast each plant did it in an average Earth bound environment.

Takeaways about plants cleaning the air

I think I'm going to keep all of my houseplants regardless of the latest findings. My house is pretty tightly sealed up over the winter time (as evidenced by the sounding of my smoke alarms every. time. I. cook). Yes I use fans and air filters. Yes I open windows when I have to. Having my leafbabies inside improves my mood. I've not measured it, but I'd expect that the evaporating water in their soil and leaves does help with the dry air in the house. I can smell them doing their job, from my citrus trees to the marigolds in the window box.

Here's where I lose my mind

One single journal article has caused an avalanche of misleading headlines all over the internet and you should be concerned. It's not "fake news" but remember where I said: "The next step should be where you go read the cited articles... I really hope you do."

If you put "Houseplants don't clean the air" into your favorite search engine you will find tens of thousands of results leading back to a single recent publication.

Personally, I feel this is misleading and unfair way to educate people. What's more accurate to say is "houseplants do clean the air, just not as fast as a HEPA filter". These articles make it sound pretty alarmist as well, as if we were relying on nothing but our dieffenbachia and Chlorophytum in the house for fresh air... or, we were some how deluded into being able to breathe better in our homes with houseplants than in our neighbors with brown thumbs.

Okay, so maybe having a few dozen leaf babies in the house between October and May makes me the male gardening equivalent of a crazy cat lady. And maybe a feel just a teensy tiney bit targeted by THIRTY THOUSAND + articles. But math is math... both articles say it so it must be true houseplants do clean the air.

Potted plants have demonstrated abilities to remove airborne volatile organic compounds

Citation: TY - JOUR AU - Cummings, Bryan E. AU - Waring, Michael S. PY - 2019 DA - 2019/11/06 TI - Potted plants do not improve indoor air quality: a review and analysis of reported VOC removal efficiencies JO - Journal of Exposure Science & Environmental Epidemiology AB - Potted plants have demonstrated abilities to remove airborne volatile organic compounds (VOC) in small, sealed chambers over timescales of many hours or days. Claims have subsequently been made suggesting that potted plants may reduce indoor VOC concentrations. These potted plant chamber studies reported outcomes using various metrics, often not directly applicable to contextualizing plants’ impacts on indoor VOC loads. To assess potential impacts, 12 published studies of chamber experiments were reviewed, and 196 experimental results were translated into clean air delivery rates (CADR, m3/h), which is an air cleaner metric that can be normalized by volume to parameterize first-order loss indoors. The distribution of single-plant CADR spanned orders of magnitude, with a median of 0.023 m3/h, necessitating the placement of 10–1000 plants/m2 of a building’s floor space for the combined VOC-removing ability by potted plants to achieve the same removal rate that outdoor-to-indoor air exchange already provides in typical buildings (~1 h−1). Future experiments should shift the focus from potted plants’ (in)abilities to passively clean indoor air, and instead investigate VOC uptake mechanisms, alternative biofiltration technologies, biophilic productivity and well-being benefits, or negative impacts of other plant-sourced emissions, which must be assessed by rigorous field work accounting for important indoor processes. SN - 1559-064X UR - https://doi.org/10.1038/s41370-019-0175-9 DO - 10.1038/s41370-019-0175-9 ID - Cummings2019