What Science Actually Says
Bringing greenery indoors has become a global trend. We keep plants on our desks, windowsills, and balconies — believing they clean the air, lift our moods, and add oxygen. The idea sounds beautiful and natural. But does it hold up to scientific scrutiny?
The popular belief that plants “purify” indoor air traces back to a 1989 NASA study. Researchers there tested a few common houseplants in small sealed chambers and found that they could remove some volatile organic compounds (VOCs) like benzene and formaldehyde. These findings spread widely and gave rise to the indoor plant boom.
However, real homes and offices are not sealed chambers. They have air movement, open doors, and varying ventilation — all of which dilute pollutants far faster than a few plants ever could.
🌱 What Really Happens Indoors
Plants do interact with air in fascinating ways. Their leaves can absorb small amounts of chemicals, roots and soil microbes can break down certain gases, and leaves can trap dust particles. Yet, when scientists calculated how many plants would be needed to noticeably clean indoor air, the numbers became staggering — dozens to hundreds of plants per square metre to match even basic ventilation rates.
In other words, one spider plant on your desk won’t make much difference to indoor air quality. Studies show that ventilation — simply opening windows or using mechanical systems — removes pollutants thousands of times more efficiently.
🌼 The Oxygen Question
Another common belief is that houseplants “increase oxygen.” Technically, they do — but the effect is minuscule. During the day, plants photosynthesize, absorbing carbon dioxide and releasing oxygen. But at night, they respire, taking in oxygen and giving off carbon dioxide, just like humans.
A controlled office study found that even 18 large ferns in a single room did not significantly change carbon dioxide levels in normal lighting conditions. The oxygen boost that plants provide is mostly symbolic — pleasant, but not physiologically meaningful.
🍃 Plants and Particulate Matter
Dust and fine particles (PM2.5) are another concern indoors. Laboratory studies show that leaves can trap particles, especially those with rough or hairy surfaces. Yet, again, the effect is small in real-world settings unless you have dense “green walls” or engineered biofilters with forced air circulation. Passive potted plants have minimal impact on PM levels.
That said, living greenery can slightly raise humidity, which may improve comfort in dry climates. People also report a sense of freshness in rooms with plants, possibly because of humidity, reduced static electricity, and the soothing psychological impact of nature.
🌻 So Are Plants Overrated?
If your goal is to reduce pollutants, yes — plants are overrated as air purifiers. But that doesn’t mean they are useless. Their real strengths lie elsewhere: enhancing well-being, lowering stress, improving concentration, and connecting us with nature. These psychological and microclimatic benefits are backed by several studies.
The best way to reduce indoor air pollution is still source control and ventilation — using low-VOC paints and cleaners, not smoking indoors, and ensuring proper air exchange. Air purifiers with HEPA and activated carbon filters are scientifically proven to work far better for particulate matter and gases.
🌿 Practical Dos and Don’ts
Do:
- Keep a few well-chosen, easy-to-maintain plants for aesthetics, humidity, and relaxation.
- Place them where they get natural light but avoid direct harsh sunlight.
- Ventilate your space daily — fresh air is the best purifier.
Don’t:
- Rely on plants alone to clean indoor air.
- Overwater or neglect them — damp soil can promote mold and worsen air quality.
- Fall for exaggerated marketing claims of “oxygen-boosting” or “air-purifying” miracle plants.
🌺 A Balanced View
Indoor plants are a wonderful addition to our spaces — they calm us, beautify our homes, and connect us to the natural world. But expecting them to act like mini air purifiers is unrealistic. The scientific consensus is clear: they make us feel better, not breathe cleaner — and that, too, has its own kind of healing power.
