Several common houseplants can absorb airborne chemicals through their leaves and roots, including peace lilies, spider plants, bamboo palms, and snake plants. A well-known NASA study in the late 1980s tested dozens of species in sealed chambers and found they removed measurable amounts of formaldehyde, benzene, and other volatile organic compounds (VOCs). But the real story is more nuanced than “buy a plant, clean your air.” How many plants you’d actually need, what they target, and how much difference they make in a normal home all matter.
How Plants Filter Airborne Chemicals
Plants pull in air through tiny pores on their leaves called stomata. When VOCs like formaldehyde or benzene enter along with carbon dioxide, the plant’s cells can break them down or shuttle them to the roots. The root zone is where the heavy lifting actually happens. Microorganisms living in the soil around plant roots, known as the rhizosphere, play a major role in degrading these chemicals into harmless byproducts like carbon dioxide and water.
Research comparing plants with and without active soil microbes found that the plant-plus-microbe system removed up to 9.5 times more formaldehyde than the plant alone. In one study, golden pothos maintained a microbial community in its root bed that continuously broke down VOCs absorbed by the roots. So when people talk about “air-purifying plants,” they’re really talking about a partnership between the plant and the billions of bacteria and fungi living in its pot.
Top Plants Tested for Air Cleaning
Not every houseplant targets the same chemicals. Here are the strongest performers from chamber studies, grouped by what they remove best:
- Peace Lily (Spathiphyllum): One of the most versatile options, removing formaldehyde, benzene, trichloroethylene, xylene, and ammonia. It’s one of the few plants tested that tackles ammonia, a common irritant from cleaning products.
- Spider Plant (Chlorophytum comosum): Particularly effective at absorbing carbon monoxide. One controlled study found spider plants reduced indoor carbon monoxide levels by 65%. They’re also easy to grow and tolerate neglect well.
- Bamboo Palm (Chamaedorea seifrizii): Effective at removing formaldehyde, benzene, trichloroethylene, and xylene. A good choice for larger rooms because it grows tall and has dense foliage.
- Dracaena species: Targets formaldehyde, benzene, trichloroethylene, xylene, and toluene. Multiple varieties exist, from the compact Janet Craig to the tall corn plant.
- Gerbera Daisy (Gerbera jamesonii): Known specifically for removing benzene and trichloroethylene. Unlike most air-cleaning plants, it’s a flowering species, though it needs more light than the others.
- Golden Pothos (Epipremnum aureum): A trailing vine that’s nearly impossible to kill. Its root system supports an especially active microbial community for breaking down formaldehyde.
Snake Plants and Nighttime Oxygen
Most plants close their stomata at night, meaning they stop exchanging gases with the room while you sleep. Snake plants (Sansevieria) are different. They use a type of photosynthesis called CAM, which flips the normal schedule: their stomata open at night and close during the day. This evolved as a water-saving strategy in dry climates, but the practical result indoors is that snake plants absorb carbon dioxide at night when other plants don’t.
This makes snake plants a popular recommendation for bedrooms, though the actual volume of oxygen one plant produces overnight is small. You’d notice the difference in air freshness more from the plant filtering stale compounds than from a meaningful boost in oxygen levels.
The Gap Between Lab Results and Your Living Room
Here’s the part most plant blogs skip. Nearly all the impressive removal numbers come from sealed chamber experiments, where a single plant sits in a small, airtight box with a known concentration of chemicals. Your home is not a sealed box. It has doors, windows, HVAC systems, and a constant exchange of air with the outdoors.
A 2019 review published in the Journal of Exposure Science and Environmental Epidemiology translated 196 chamber experiments into a standardized air-cleaning metric. The results were sobering. The median plant cleaned just 0.023 cubic meters of air per hour. To match the VOC removal that normal ventilation already provides in a typical building, you would need between 10 and 1,000 plants per square meter of floor space. For a standard living room, that could mean hundreds of plants.
This doesn’t mean houseplants do nothing. It means that a few potted plants on a shelf won’t replace opening a window or running an air purifier. The original NASA guideline suggested one plant per 100 square feet as a starting point, but that recommendation was designed for sealed spacecraft environments, not homes with regular air exchange. Plants contribute a small, passive layer of filtration. They’re better thought of as a supplement to good ventilation, not a substitute for it.
What Plants Actually Do for Your Indoor Environment
Beyond VOC removal, houseplants affect your space in ways that are easier to notice. Through transpiration, plants release water vapor from their leaves, gently raising indoor humidity. This can be genuinely helpful in dry climates or during winter when heating systems parch the air. Grouping several plants together amplifies this effect. If you set their pots on a tray of gravel and water, the evaporation adds even more moisture to the room.
There’s a tradeoff, though. Overwatering or poor drainage creates conditions for mold growth in the soil, which can release spores into the air and worsen allergies. Keep pots well-drained, avoid letting soil stay soggy, and don’t pack plants into a small, poorly ventilated space. The goal is a few healthy, well-maintained plants, not a damp jungle corner.
Pet Safety With Air-Cleaning Plants
Several of the most popular air-cleaning plants are toxic to dogs and cats if chewed or ingested. The ASPCA lists peace lilies, golden pothos, dracaena, snake plants, Chinese evergreens, and dieffenbachia as toxic to dogs, and most of these are harmful to cats as well. Symptoms typically include mouth irritation, drooling, vomiting, and difficulty swallowing.
If you have pets, safer alternatives include spider plants, bamboo palms, and Boston ferns, which are non-toxic and still appear on air-cleaning lists. Placing toxic plants on high shelves or in rooms your pets can’t access is another option, but cats in particular tend to find their way to any plant they’re curious about.
Getting the Most From Your Plants
If you want to maximize whatever air-cleaning benefit plants provide, a few strategies help. First, prioritize root health. Since soil microbes do most of the pollutant breakdown, keeping roots in well-aerated, healthy soil matters more than having the biggest leaves. Repot plants when they become root-bound, and use a quality potting mix that drains well.
Second, spread plants across rooms rather than clustering them all in one spot. A peace lily in the kitchen (where cooking releases VOCs), a spider plant in the living room, and a snake plant in the bedroom covers more ground than six plants on the same windowsill. Third, keep leaves clean. Dust buildup on leaf surfaces blocks the stomata and reduces the plant’s ability to exchange gases. A damp cloth every few weeks is enough.
Finally, pair plants with common-sense ventilation. Open windows when weather allows, use exhaust fans in kitchens and bathrooms, and consider a HEPA air purifier if you’re dealing with specific pollutant concerns. Plants add a pleasant, low-cost layer to your indoor air strategy, but they work best as part of a bigger picture.