Every list of the best indoor plants says the same thing: put a snake plant in the bedroom and it will clean your air, because NASA proved it. It is one of the most repeated facts in gardening. It is also mostly a misunderstanding.
The short answer
In small sealed test boxes, plants did remove some chemicals from the air. In a real room, ordinary air exchange through windows and doors does that job far faster. A 2019 review estimated you would need 100 to 1,000 plants per square metre of floor to keep up. Keep plants for joy, not for air.
Where the claim comes from
In 1989, NASA researchers led by Bill Wolverton tested common houseplants as a way to clean air in sealed spaces like a space station. They put plants into small airtight chambers, added chemicals such as benzene and formaldehyde, and measured how fast the levels fell. They did fall, and the study became a legend.
The catch: a box is not a room
Those test chambers were tiny, typically around a cubic metre, roughly the space taken up by a large armchair, and completely sealed. A real home is neither. Air is always leaking in and out through windows, doors, gaps and fans, and that exchange carries pollutants away.
In 2019, Bryan Cummings and Michael Waring at Drexel University went back through a dozen studies spanning 30 years and asked a simple question: how much clean air does a plant actually deliver, compared with a room's normal air exchange? In every case they could calculate, the plants were far slower.
Their estimate: to match a building's ventilation, or even just a couple of open windows, you would need between 100 and 1,000 plants for every square metre of floor. As Waring put it, plants โdon't actually clean indoor air quickly enoughโ to make a difference.
So what does clean the air at home?
- Fresh air, when the air outside is good. Opening windows on opposite sides of a room moves air fast.
- Exhaust fans in the kitchen and bathroom, where smoke and moisture start.
- On bad air days, which many Indian cities see in winter, check the AQI first. When outdoor air is poor, keep windows shut and use a purifier. No number of pots replaces it.
Why plants are still worth it
None of this makes houseplants pointless. It just means we keep them for the right reasons. A green corner makes a room feel calmer and more alive. Looking after something that grows, and watching a new leaf open, is quietly satisfying. Those are reasons enough, and they are true.
If you want plants that forgive a few mistakes while you learn, our Plant Clinic can help you pick and care for them.
Sources
- Drexel University (2019), Study: Actually, potted plants don't improve air quality
- Cummings, B. and Waring, M. (2019), Potted plants do not improve indoor air quality: a review and analysis of reported VOC removal efficiencies, Journal of Exposure Science and Environmental Epidemiology
- Wolverton, B. and others (1989), Interior landscape plants for indoor air pollution abatement, NASA
