Do house plants clean indoor air?
The idea that house plants filter and clean indoor air is at best a mini-truth, and at worst a total myth, and like any pseudo-science health trend, it can have a negative impact as well. Providing false solutions to human health issues gives people a false sense of security. Having plants in your home provides quality of life and a connection to nature but functionally speaking, they do next to nothing to improve air quality.
Just as some questionable home remedies, homeopathic solutions and anti-vaccine propaganda can be counterproductive to maintaining health, succumbing to these internet myths and relying on plants to clean your air may worsen the indoor air quality in your home. It’s far better to follow practical and proven methods and guidelines, such as those laid out in home rating systems like LEED. One example of something the internet has spread around as a truth is using coffee grounds in the garden - discover here why it's such a bad idea.
This popular internet rumor stems from a NASA study in 1989 that concluded that if humans were to live in small hermetically-sealed spaces, plants offered a potentially affordable solution to reducing indoor air pollution.
This anecdotal conclusion has grown to epic proportions among home décor websites to the point where there are even recommending specific plants in specific rooms for their particular characteristics; the following examples were easily found on the web –
The best air purifying plants are apparently....
• Bamboo palm and spider plants in the kitchen to remove formaldehyde, xylene, and toluene, which can be found in certain kitchen appliances and furniture.
• Snake plants in the bedroom because they absorb CO² in the day, release oxygen at night, & who doesn't like snakes in the bedroom?
• Boston ferns in the basement because they like cool, moist areas with no direct sunlight.
That is all complete nonsense. If your basement has high humidity levels, you have a problem that a fern isn’t going to solve. High humidity levels in basements leads to mold and mildew, and due to the natural stack effect of air flow, mold spores from your basement will find their way into the upper floors of your home.
The first step to dealing with basement humidity is to get a dehumidifier and try to keep the Relative Humidity level (RH) to below 50%. See our pages on why basements are moldy and how to fix them for more in-depth basement improvement advice than ‘buy a fern’.
Will putting a bamboo and spider plant near your kitchen help remove toxins from the air? No more than walking past a dentist office will whiten your teeth. There is more dust and chemicals being filtered through your nose than the plant you may be standing beside.
Beyond the trivial contribution plants make to home air quality, we find the idea that putting specific plants in specific rooms for added benefit to be particularly amusing, given the air movement in homes due to ventilation equipment.
An ideal HVAC design for homes would include a ventilation intake near the kitchen, which would pull out between 100 and 200 CFMs (cubic feet per minute) of air locally; there is no plant that can process that volume of air.
Snake plants flood bedrooms with oxygen & promote sleep - or do they?
Will a snake plant in the bedroom provide me with oxygen? If you are an aphid sitting on a leaf, yeah probably a bit, but for our human readers - a bedroom fresh air vent may be a better bet as it should be fed about 10-20 CFMs of fresh air. But put one in there anyway, plants are a lovely sight to see as you wake up in the morning.
In response to the internet wave of bogus information about plants cleaning air, the Environmental Protection Agency (EPA) conducted its own studies and determined that to achieve the same rate of cleanup as in NASA's Chamber Studies, it would take more than 680 plants to remove toxins in a 1,500 sq. ft house.
The EPA study was confirmed by many researchers including Michael Waring, Richard L. Corsi and Elliot Gall, who arrived at these conclusions after analysing 195 studies examining indoor plants and their ability to filter air, produce oxygen and remove toxins. They concluded that some plants eliminate VOCs better than others, but when put in large rooms, their effects are practically inexistent.
“We decided to study it more in-depth in response to all the internet articles and wellness blog posts that tout plants as an indoor air quality magic bullet,” says Michael Waring, an environmental engineer and indoor air quality expert at Drexel University.
Another study showed even less air quality benefits from house plants, and concluded that it would take approximately 1,000 plants in a 10 square foot area to achieve the improvement in air quality that can be attained with a conventional ventilation system with high efficiency MERV filters.
André Fauteux, publisher of the Quebec magazine La Maison du 21e siècle spoke with former NASA researcher BC Wolverton, who was involved with the initial study, and who acknowledged that - “reducing pollutants at the source and ventilation have a greater depolluting impact on air quality than the use of plants. The impact of plants is only noticeable in a perfectly waterproof and non-ventilated building, like a space capsule." This may come as a revelation to all those pseudo-sustainable construction websites, but homes and space capsules are very different.
How to improve indoor air quality in homes?
To solve a problem, you need to identify the problem and, in terms of air quality in a home, that means determining what are the common contaminants found in indoor air and what is the best way to remove them. From there you should, whenever possible, make eliminating the source AT the source the priority, then implement an effective system for removing any remaining contaminants from the air.
Always choose non-toxic building materials, and low or zero VOC paints and finishes.
Avoid chemical cleaning agents; read here about how to clean a home using non-toxic safe cleaners.
Avoid adding scents; read here about the impact of fragrances on indoor air quality.
Have air-handling units regularly maintained, and keep your HRV operating clean and efficiently.
Choose the right air filter for your home with the appropriate MERV rating.
Home air quality is a growing issue as homes become more energy efficient and airtight. Ventilation systems are now standard requirements in most national and regional building codes and serve to provide fresh air to indoor environments, but we should also be aware of the types of toxins we are introducing through building materials. With the current issues of airborne viruses as well, it's never been more important to choose the right air filter and furnaces and ventilation units to protect against viruses and remove allergens.
Ventilation systems for home renovations
If you are looking to add a ventilation system to an existing home or for a new addition, while it’s not always a feasible solution to bring ductwork to the new living area, there are ductless HRVs and ERVs (heat recovery and energy recovery ventilators) that can be added without great hassle to improve indoor air quality.
Ductless ventilators simply require feeding a low-voltage wire to units, so no major renovation is required and wires can be fairly easy to hide. See our DIY ductless HRV installation video here.
About the author:
Emmanuel Cosgrove built the first LEED Platinum home in Canada, he is a co-founder of Ecohome, a LEED for Homes Provider, LEED Green Rater, recipient of the 2016 Green Building Champion Award from the CaGBC, and a contributor to the LEED for Homes Rating system.