Best Indoor Plants for Air Quality: 15 Plants Rated for Light, Water, and Pet Safety

Sep 24

Written By Ivy Ham

University labs in Australia, Korea, Thailand, and the United States have spent the last 25 years putting houseplants in sealed chambers and measuring which chemicals they pull out of the air. The plants do absorb benzene, formaldehyde, toluene, and other volatile organic compounds (VOCs), and a large share of the work is done by microbes living in the potting mix. The open question is how much that adds up to in a room with doors, windows, and a furnace fan. This guide covers sixteen plants, what each one was tested against and by whom, whether it is safe around cats and dogs, and how much light, water, and attention it needs, scored 1 to 5 with icons so you can compare at a glance.

Key takeaways

Potted plants remove VOCs in sealed chambers, and independent studies show the root zone and its microbes do half the work by day and nearly all of it at night.
A 2020 engineering review found ordinary ventilation dilutes VOCs far faster than plants absorb them; a 2009 Korean room study measured a 6 to 7% drop in formaldehyde when plants filled 1% of the room's volume.
Six plants in this guide are listed as non-toxic to cats and dogs by the ASPCA: spider plant, Boston fern, bamboo palm, areca palm, kentia palm, and wax plant (Hoya).
Snake plant, pothos, peace lily, English ivy, dracaena, rubber plant, Chinese evergreen, aloe, chrysanthemum, and weeping fig are all on the ASPCA toxic list.
Each plant is rated 1 to 5 for light, water, and ease of care, with a pet-safety badge and a note on whether its air data comes from an independent lab.

This article is for education only. It is not medical or veterinary advice and does not diagnose or treat any condition. Plant toxicity ratings come from the ASPCA Animal Poison Control Center database and can change; a plant listed as non-toxic can still cause vomiting if a pet eats enough of it. If a pet chews any houseplant and shows symptoms, contact your veterinarian or an animal poison control line. If you have asthma, chemical sensitivities, or a known indoor air problem such as mold or radon, plants are not a substitute for testing, ventilation, or a proper filter.

Do houseplants actually clean the air?

Evidence: mixed. Chamber studies from several independent universities show real VOC uptake; the two room-scale analyses disagree on whether the effect is large enough to matter.

The chamber method is simple. A potted plant goes into an airtight box, a single chemical is injected, and samples are taken over hours or days. A Korean government horticulture lab ran that test on 86 species against formaldehyde and found ferns removed it fastest as a group, with the Japanese royal fern 50 times faster than the slowest species, a Dracaena.^[2] A University of Georgia group screened 28 species against five aromatic compounds and found English ivy, wax plant, asparagus fern, purple waffle plant, and purple heart removed all five.^[5] A University of Technology Sydney team showed that potting mix with its microbes removed benzene on its own, and that removal sped up after two to four days of exposure as the microbial community adapted.^[6] The Korean lab then separated leaves from roots and found the root zone did about half the formaldehyde removal by day and nearly all of it at night.^[4] These results came from four countries with no shared funding, so the basic finding that potted plants absorb VOCs is not in doubt.

Most of the plant lists circulating online come from an earlier 1989 NASA chamber study that was co-funded by a plant-leasing trade association, which is why its results were promoted so heavily; the independent labs above have since tested most of the same plants.^[13]

The problem is scale. In 2020, Bryan Cummings and Michael Waring at Drexel University pulled the data from twelve chamber studies and converted each result into a clean air delivery rate, the metric used to rate mechanical air purifiers.^[1] Their math showed it would take between 10 and 1,000 plants per square meter of floor space to compete with a building's air handling system, or even a couple of open windows. A sealed chamber has no air exchange at all, so a plant that clears half the formaldehyde in a day looks impressive there. A living room swaps its full volume of air with the outdoors every hour or two, which does the same job many times faster.

The one study that measured plants in an actual room rather than a chamber came from the same Korean lab. They placed pothos, rosemary, and gardenia in a room at 3, 6, and 9% of its volume and measured formaldehyde drops of 31, 48, and 67%. Scaled down, plants filling 1% of a room's volume reduced formaldehyde by 6 to 7%. The measured removal in the room was one twentieth of what the chamber test had predicted.^[3] That is a real effect, and it is also a small one that took a room crowded with plants to produce.

So the practical position is this. Plants are not an air purifier and should not be bought as one. Ventilation, removing the source of the chemical, and a HEPA or carbon filter do the measurable work. Plants add humidity through transpiration, they give a sealed winter home some living biology, and the microbes in their soil break down small amounts of what lands on them. Researchers working on active green walls, where a fan pushes room air through the root zone, have measured meaningful removal rates, and that is where the field is heading.^[11] A pot on a shelf is the passive version of the same idea.

How to read the ratings

Evidence: horticultural practice. Care scores are drawn from extension-service growing guides and common experience, not from trials.

Each plant card below carries three scores and a pet badge.

Light (sun icon), 1 to 5. 1 means it tolerates a dim corner or a north window. 3 means bright indirect light, a few feet from an east or west window. 5 means several hours of direct sun.
Water (droplet icon), 1 to 5. 1 means let the soil dry out completely between waterings. 3 means water when the top inch (2.5 cm) of soil is dry. 5 means keep the soil evenly moist and never let it dry.
Ease of care (leaf icon), 1 to 5. 1 is fussy and drops leaves when conditions shift. 5 survives neglect, low light, and missed waterings.
Pet badge (paw icon). Green means the ASPCA lists the plant as non-toxic to cats and dogs. Rust means it is on the ASPCA toxic list.^[12]

The "tested against" line on each card names only the chemicals that plant was measured against in a published chamber study, and which lab did the measuring. Where the only data comes from the 1989 NASA list or from a later popular book by its author, the card says so. It does not mean the plant will lower those chemicals in your home.