Do plants really clean the air in our homes? And do pets actually make it worse? These are widely held beliefs, but when we look at the scientific evidence, the story changes quite a bit. Potted plants are not natural air purifiers, and dogs are not dangerous little emitters. Meanwhile, perhaps surprisingly, humans remain the biggest “polluters” of our own homes.
Plants don’t clean as much as we think
The idea that plants clean the air comes from studies conducted in sealed chambers. In a normal home—with windows, airflow, and large volumes of air—that effect practically disappears.
Scientific reviews agree that dozens, or even hundreds, of plants per square meter would be needed to achieve a noticeable reduction in pollutants such as formaldehyde or benzene. These harmful organic compounds may be present in the air and often come from traffic, tobacco smoke, or building materials.
The effect of indoor vertical gardens
However, there is an interesting nuance: indoor vertical gardens, which concentrate many plants on the same surface, can achieve measurable improvements under certain conditions. A 2021 study showed reductions of CO₂ by 12–17% and PM2.5 (particles smaller than 2.5 microns) by 8–14% in a corridor with a plant wall compared with an identical one without it.
Along the same lines, a 2026 study in an administrative building found that near the vertical garden, formaldehyde levels decreased by up to 40%, although the effect disappeared just a few meters away.
That said, these systems require good design and maintenance. The same study detected more mold spores in areas where humidity was high or maintenance was not optimal.
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So while a single plant does not significantly clean the air, a large and well-maintained vertical garden in specific areas can provide modest benefits.
Plants also offer microclimatic benefits (humidity, comfort, slight temperature reductions) and positive psychological effects. Therefore, they should not be considered air filters, but rather elements that contribute to well-being.
What about dogs? Do they release many polluting emissions?
As for pets, a recent study measured for the first time the real emissions of dogs and humans in a controlled chamber. According to the results, a large dog emits approximately the same amount of CO₂ and ammonia as an adult human, while a small dog produces considerably less.
Secondly, the particles they release are of the same order as those produced by humans, except in very active dogs that stir up more dust.
The main difference is that these animals bring microbes from outside, which increases the microbial diversity in the home. However, this is not necessarily negative, as some studies suggest it may support immune system development.
The fact that changes everything: how much do humans emit?
Much more than any dog—and certainly more than any plant. A 2022 study showed that each person emits more than 2,000 micrograms per hour of volatile organic compounds, a figure that doubles when there is ozone in the outdoor air because it reacts with the oils on our skin.
In addition, when we move around, we stir up dust, fibers, and particles. The biggest impact on indoor air therefore comes from our own activities: cooking, cleaning, showering, using air fresheners, or simply being present.
Read more: High levels of indoor air pollution are raising alarms
It is important to note that not only the number of particles matters, but also how they react in our bodies. In this sense, those associated with dogs tend to be larger and less reactive than the fine particles of urban origin or those generated during cooking.
So… is it better to have plants or pets?
There is no need to choose. Plants—especially when grouped into well-designed vertical gardens—can provide small local improvements and a great deal of well-being. Pets actually emit less than we think. And the air in our homes depends much more on us than on them.
The recipe remains the same: ventilate, reduce sources of pollution… and enjoy a home full of life.
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