Especially with the push for ultra energy efficient homes and the utter sealing from the outside environment, I felt like this was a good time to revisit a way to purify indoor air with no energy expenditure. Coworkers in every office in which I have worked found my abundance of desk plants strange yet a somewhat welcome change of scenery from the cheesy motivational posters common to that environment. Loathing being indoors and lacking trust in building management companies to adequately change air filters, I started reading the NASA Clean Air study in about 2010. Ever since reading the study I have had a handful of Mother-In-Law’s Tongue on every desk which I have worked. They have to be the hardest plant to kill that I have ever experienced.
Summarized, NASA studied plants with the intent of sustaining the air supply in the space station as well as sequestering airborne chemicals. They compiled a list of plants that successfully remove benzene, formaldehyde and trichloroethylene. BC Wolverton, an author on the original NASA study continued his research and experimentation with a 1993 Research Paper and a 1996 book: <Wolverton, B. C. (1996) How to Grow Fresh Air. New York: Penguin Books>. Together these three publications yield a large list of plants that remove one or more of the 6 common household airborne pollutants that were studied. The chart can be found on Wikipedia.
After using the cabin on my farm temporarily, I really enjoy the fresh air. Except when there is none. Keeping the cabin warm in the winter with the woodstove and closed windows got me thinking. Afterall, the most dangerous aspect of cigarettes is not so much what companies put into them but the direct inhalation of the chemicals produced from the combustion of carbon matter. With very little ventilation in my cabin in the winter, most of those chemicals are trapped right inside where I sleep.
So I decided to revisit my once familiarity with these studies.
I’ve tried a handful of plants in the studies but have settled on 3 specific species. Some of the plants are short lived and need continuous replacement or very specific growing conditions like the Florist’s chrysanthemum (Chrysanthemum morifolium). Plants like these required more attention than I am willing to give this project. I like the plants that are mostly set and forget. They do their air purification happily as long as I water occasionally.
It is recommended to have 1 mature plant per 100 square feet of space that needs purification. That is quite a bit and another benefit I see to using a minimal, 200 square foot cabin and a sub 400 square foot house I aspire to build.
3 species I recommend for ease of growth
Mother in Laws Tongue aka Snake Plant (Sansevieria trifasciata ‘Laurentii’) The only thing that killed one of these in my care was a miscommunication with a family member stemming from my neglect of the still healthy plant. Otherwise it survived years of neglect with sporadic watering and no fertilization. It will remove benzene, formaldehyde, trichloroethylene, xylene and toluene but not ammonia.
Peace Lilly (Spathiphyllum ‘Mauna Loa’) This is a classic houseplant that is easy to care for and removes all chemicals studied: benzene, formaldehyde, trichloroethylene, xylene and toluene, ammonia.
Red-edged dracaena (Dracaena marginata) This one was never readily available when I looked so I have not grown it yet. However I threw one in an order I placed at a nursery. It removes the same 5 chemicals as the Mother in Law’s tongue.
Additionally, these studies found that the microbes in the potting soil further removed chemicals like benzene. I’ve even seen one study where activated charcoal was mixed into the soil and a cage fan pumped air into the soil allowing the chemicals trapped in the charcoal to fertilize the plants like ammonia used in aquaponics. This may be a bit beyond my engineering skills but I may try and rig up a small solar setup to drive the fan when time allows.
To conclude, these plants can help preserve your health. After all, indoor air tends to be 2-5 times (sometimes up to 100!) more polluted than outdoor air. Without using a bit of energy, plants can remove the most common and problematic pollutants. A perfect project for kids, just provide water and occasional fertilizer!