Several common houseplants can absorb airborne chemicals like formaldehyde and benzene in laboratory settings, but the real-world effect is far smaller than most people expect. The science behind “air-purifying plants” is more nuanced than the viral lists suggest, and understanding what plants can and can’t do will help you set realistic expectations while still enjoying their genuine benefits.
Where the Idea Comes From
The concept of air-cleaning houseplants traces back to research led by Bill Wolverton at NASA in the late 1980s. Wolverton screened about a dozen common houseplants, from gerbera daisies to bamboo palms, testing their ability to remove household toxins like formaldehyde from a sealed chamber. The results were impressive: certain plants broke down volatile organic compounds (VOCs) and even pathogenic bacteria, converting pollutants into new plant tissue through their root systems. That study became one of the most cited pieces of houseplant advice on the internet.
The catch is that Wolverton’s experiments used small, sealed chambers, nothing like a living room with open windows, HVAC systems, and constantly refreshed air. More on that gap between lab and real life below.
Plants With the Strongest Lab Results
Spider Plant
Spider plants are one of the most studied species for formaldehyde removal. Lab measurements show their leaves break down formaldehyde at a rate of about 13 micrograms per gram of leaf tissue per hour. They’re also extremely easy to grow, tolerate low light and inconsistent watering, and produce offshoots you can propagate endlessly. For a beginner looking to start somewhere, spider plants are hard to beat.
Peace Lily
Peace lilies performed well in Wolverton’s original screening and continue to show up in newer research. In a 2024 study testing benzene absorption, peace lilies achieved a purification rate of 57.5% at moderate benzene concentrations, with an average rate of about 44% across different exposure levels. They also thrive in lower light than most flowering plants, making them practical for rooms without large windows. One caution: peace lilies are toxic to cats and dogs if chewed or ingested.
Snake Plant
Snake plants have an unusual trick that sets them apart. Most plants open the tiny pores on their leaves during the day and close them at night. Snake plants do the opposite, using a type of photosynthesis called CAM (Crassulacean Acid Metabolism) that evolved in dry climates to conserve water. At night, they open their pores, absorb carbon dioxide, and store it as an organic acid in their leaf cells. During the day, they close their pores and use that stored carbon dioxide for photosynthesis. The practical result is that snake plants release oxygen at night, which is why they’re often recommended as bedroom plants. They’re also nearly indestructible, tolerating neglect, low light, and dry air.
English Ivy
English ivy stands out for mold reduction rather than chemical removal. In experiments presented to the American College of Allergy, Asthma, and Immunology, English ivy reduced airborne mold by 60% within six hours. After twelve hours, more than 78% of airborne mold was gone from the air around the plant. If you live in a humid climate or a space prone to mustiness, ivy is worth considering. It does need bright, indirect light and consistent moisture to stay healthy indoors.
Other Notable Species
Wolverton’s original research and subsequent studies also flagged bamboo palms, rubber plants, Boston ferns, golden pothos, and gerbera daisies as effective in sealed-chamber tests. Boston ferns are particularly good at raising humidity levels, which can help with dry winter air. Golden pothos, like spider plants, is nearly impossible to kill and grows well in low light. Gerbera daisies add color but are trickier to keep alive indoors long-term.
What Actually Does the Cleaning
A common assumption is that leaves absorb pollutants the way a sponge soaks up water. The reality is more interesting. Root-associated microbes do much of the heavy lifting. Bacteria colonizing the root zone consume VOCs, breaking them down into carbon dioxide, water, and biomass. Research on plant-based biofilters shows that when roots are exposed to contaminated air over time, specific bacterial communities shift and proliferate in response to the chemicals present. One genus of bacteria, Hyphomicrobium, was found to thrive on plant roots exposed to VOCs compared to roots grown in clean conditions.
This means the soil and root system matter as much as the foliage. Plants potted in rich, well-aerated soil with healthy root systems will do more than a plant sitting in compacted, waterlogged dirt. Some commercial “biowall” systems exploit this by actively drawing room air through the root zone, dramatically increasing the contact between pollutants and the microbes that break them down.
The Reality Check: Plants vs. Ventilation
Here’s the part most plant blogs skip. A 2019 review published in the Journal of Exposure Science and Environmental Epidemiology analyzed 196 experimental results from 12 published studies and translated them into clean air delivery rates (CADR), the same metric used to rate mechanical air purifiers. The median single-plant CADR was 0.023 cubic meters per hour. To match the VOC removal that normal outdoor-to-indoor air exchange already provides in a typical building, you would need somewhere between 10 and 1,000 plants per square meter of floor space.
That’s not a typo. In a 10-by-10-foot room, you’d potentially need hundreds of plants to achieve what opening a window accomplishes. A separate study on office buildings found no significant reduction in CO2 concentration after introducing indoor plants, though relative humidity did increase measurably.
This doesn’t mean plants are useless. It means a few pothos on a shelf won’t meaningfully detoxify your home. The sealed-chamber results from NASA are real, but they don’t scale to normal living spaces with natural ventilation.
What Plants Genuinely Improve
If the chemical filtration effect is modest in real rooms, why do so many people report feeling better with plants around? Several things are at play. Plants reliably increase relative humidity, which can ease dry skin, scratchy throats, and static electricity during winter months. The psychological benefits are well documented: having greenery in your space reduces perceived stress and improves mood. And in poorly ventilated spaces with very high concentrations of specific pollutants (a freshly painted room, new carpet off-gassing formaldehyde), a cluster of plants can make a marginal but real contribution, especially if air flow passes near the soil.
For meaningful air quality improvement, plants work best as a complement to good ventilation, not a replacement. Open windows when weather permits, run exhaust fans, and consider a mechanical air purifier if you’re dealing with specific pollutant concerns like wildfire smoke or high VOC levels from renovation.
Pet Safety
Several of the most popular air-purifying plants are toxic to cats and dogs. Peace lilies, English ivy, and Chinese evergreens all contain compounds that cause oral irritation, drooling, vomiting, or worse if ingested. Snake plants are mildly toxic as well.
If you have pets, safer options include spider plants, Boston ferns, and certain palms like the areca palm and parlor palm. The ASPCA maintains a searchable database of toxic and non-toxic plants that’s worth checking before you buy anything new.
Getting the Most From Your Plants
If you want to maximize whatever air-cleaning benefit houseplants provide, a few strategies help. Use more plants with larger leaf surface area, since gas exchange happens through leaf pores. Keep soil healthy and well-draining so root microbes can thrive. Place plants closer to potential pollution sources like new furniture, printers, or cleaning product storage areas. And keep leaves clean by wiping them with a damp cloth every few weeks, since dust buildup can clog the pores that absorb gases.
A reasonable starting point for a typical room is three to five medium-sized plants. You won’t transform your air quality, but combined with decent ventilation, you’ll get a small filtration boost along with the humidity and psychological benefits that are better supported by real-world evidence.