Domestic chemical ecologies have both many toxicant sources and many toxicant sinks. Formaldehyde slowly and silently off gasses from engineered woods, carpets, and permanent press clothing. Some of these silent emissions waft out open windows. Others are absorbed by human bodies or the bodies of companion species. Others still are metabolized by decorative indoor plants and the microbes that inhabit their roots.

Since the 1990s we have been hearing promises of plant-based air filters. See, for example, this patent filed in 1993. Some critics (see this 2009 critical review) find fault in the claim that plants-on-their-own can clean indoor air and state that the average home would need 680 plants to adequately scrub the air of toxicants.


Image by Jeff Warren

Research indicates that it is not so much that different plants remediate the air differently, but that different plants cultivate different rhizospheric conditions by their root exudates and root autolysis. Plants with quantitatively more bacteria dwelling in their rhizosphere won’t remediate as much atmospheric formaldehyde as plants with fewer overall microorganisms amongst their roots but more gram-negative rods.

The formaldehyde removal capacity of plants and their bacterial companion species increases as exposures increase, and over time the bacteria appear to “acquire an increased taste” for exposed toxicants and up-regulate their metabolism. Phyto-bio remediation does not appear to be reaction-limited but diffusion-limited. The amount of air breezing through the roots and across the leaves of indoor plants is minimal.

The Public Lab Indoor Air Remediation Kit, of which I have been leading the development, builds upon these observations that, at least in theory, increasing the airflow through the root system could increase the remediation capacity of plants by upwards of 200 fold. Plant air scrubbers would not require the intermittent replacement replacement of filters but would become more efficient overtime.

Plants manage decomposition underground by providing sugars to symbiotic and beneficial fungi and bacteria in order to manage root growth and decomposition. Plants spend more energy below ground than above ground, and seasonally grow and kill roots just like leaves. We’re piggy backing on this process, using plant-managed colonies of beneficial bacteria to scrub formaldehyde, a naturally occurring product of decomposition.

While there is evidence on both sides to indicate either the efficacy or inefficacy of plants-on-their-own as indoor air filters, there have been no published studies on the efficacy of plant systems with increased airflow, like the prototype offered by Public Lab.

More info: Low-cost phyto-bacterial VOC degradation system (Air Purifier): concept, iteration #1, iteration #2, DIY instructions.  The hardware is currently being refined by french designer Christophe Guerin.



Medium Term

Remediation of ongoing contamination is not a sustainable intervention and will never reach the scale of the problem.  Currently, there are no low-cost and robust means of assessing formaldehyde, the most common indoor air toxicant. To address the immense need for means of validating embodied awareness of toxic atmospheres, I’ve been working for several years developing inexpensive formaldehyde test kits.

Here are DIY instructions on how to build our first kit. The colorimetric detection tube that we utilized in the kit, following a peer-reviewed method, presented serious co-contamination problems when Gretchen Gehrke and I attempted to validate it in collaboration with Rhode Island Department of Health.

Since then, we’ve been been working with a team at Ohio State University, the Building Energy and Environmental Systems Laboratory (BEESL) at Syracuse University and a community group in Georgia to develop a free smart-phone app that can read the color changes on a ~$5 treated slip of paper. See our website for more information, our GitHub (code) is here.


Long term

See Aerocene.org for more information about the Aerocene Project that works on a timescale that approaches the utopic.


Filling up a solar balloon atop a glacier in Paradise Bay, Antarctica.  

Odds and ends

“Where We Breathe” environmental health and community organizing software: overview + Github (code).

Together with collaborators on a gas patch in north east PA, we developed a community air monitoring protocol and data sheet for use natural gas compressor stations.

%d bloggers like this: