Houseplants are credited with a lot: purifying the air, "absorbing radiation" from computers, bringing good energy. Which of these claims does science support, and which are just pleasant myths? Here is how plants really affect indoor air, wellbeing and mood — and what to keep in mind if you have children or pets.
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The main myths and facts about houseplants
Do plants purify indoor air?
The idea goes back to a 1989 NASA study: in small sealed chambers, plants reduced levels of some volatile organic compounds such as benzene and formaldehyde. But a living room is not a sealed chamber. A 2019 review that re-analysed dozens of experiments found that matching normal air exchange through windows and ventilation would take 10 to 1,000 plants per square metre of floor.
Bottom line: plants make a room more pleasant, but they don't replace opening windows and ventilation.
Plants release water through their leaves, so a group of large plants can raise humidity slightly — noticeable in winter when the heating is on. Even so, the effect is smaller than a humidifier's. Which plants suit a bedroom and which to move out: bedroom plants.
Mood and wellbeing
This is where plants have more solid benefits. Studies link indoor greenery and caring for plants with feeling calmer, lower perceived stress and better concentration. The effect is modest but real: watering, repotting or simply looking at greenery is a good way to switch off.
Which houseplants clean the air best: the NASA list
These are the plants that most often top “air purifier” rankings — mainly thanks to the 1989 NASA study. Remember: the effect was real in a sealed chamber but very modest in a real room.
Spider plant — the most cited in studies: reduced formaldehyde in test chambers. Fast-growing, cat-safe and easy to propagate from plantlets.
Snake plant — takes in CO₂ at night thanks to its special photosynthesis; tolerates shade and infrequent watering.
Peace lily — reduced several VOCs in NASA tests and transpires plenty of moisture; flowers in partial shade. The sap irritates, so keep away from pets.
Pothos — a fast-growing vine often included in such lists; almost unkillable.
Dracaena — several species (marginata, fragrans) were in the NASA experiment; good for large rooms.
Parlour palm — a palm for partial shade that raises humidity; pet-safe.
Weeping fig — appears in the lists but can trigger allergies — allergy sufferers should pick another.
English ivy — reduced benzene in experiments; a trailing plant for cool, bright rooms.
Boston fern — the best fern for adding humidity, but it needs regular misting.
Aloe — compact for a sunny windowsill; the gel helps with minor burns.
Popular myths
"Plants in the bedroom steal oxygen at night." Plants do respire at night, but they use a negligible amount of oxygen compared with a person. There's no danger.
"Snake plants release oxygen at night." They use a special type of photosynthesis, opening their pores at night to take in carbon dioxide. But this makes no noticeable difference to the air in a room.
"A cactus by the monitor absorbs radiation." No — plants don't shield electromagnetic fields.
"Flowers bring good energy or bad luck." These are superstitions, not plant properties.
How to actually improve indoor air
Ventilation — 5–10 minutes several times a day beats any number of plants.
Kitchen and bathroom extractor fans — remove moisture and combustion products.
An air purifier with a HEPA filter — for dust and pollen, especially for allergy sufferers.
A humidifier in winter — keep humidity at 40–60%; plants help a little.
Plants are a pleasant extra: they decorate, add a little humidity and lift your mood. Just do not overwater — damp soil encourages mould and fungus gnats.
Easy-going houseplants
If you want greenery without the fuss, choose forgiving plants:
Snake plant (Sansevieria) — tolerates shade and infrequent watering.
Toxic plants — dieffenbachia, peace lily, monstera; lilies are especially dangerous for cats. With toddlers or pets at home, keep such plants out of reach or choose safe ones.
Allergies. Weeping fig sap can cause allergies, and mould can grow in soggy compost and saucers.
Tobacco smoke is not "cleaned" by plants — see which ones at least cope with it in our article on houseplants and tobacco smoke.
More than anyone could fit in a flat. For clean air, rely on opening windows, ventilation and an air purifier.
Can I keep plants in a child's room?
Yes, if you choose non-toxic plants and place pots where a child can't knock them over.
Which houseplants clean the air best?
Rankings usually name spider plant, snake plant, peace lily, pothos, dracaena and parlour palm — but in a flat the effect is modest; ventilation and purifiers do far more.
How many plants would it take?
A 2019 review estimated 10 to 1,000 plants per square metre to match normal ventilation, so plants complement airing rather than replace it.
Author: Maria Svitlovir
Graduated from Taras Shevchenko National University of Kyiv, Institute of Biology and Medicine (2001). BSc in Biology, MSc in Horticulture. Writes about plants, works at a garden centre selecting and repotting plants, and contributes to plant reference guides.
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