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Indoor plants can only saturate the air with oxygen and replace air filters in a small, fully enclosed space. In a well-ventilated urban apartment, it is improbable for them to do so. Nonetheless, indoor greenery provides other benefits such as promoting relaxation and regulating the air’s humidity level.
Why is it believed that plants improve the air?
Through the process of photosynthesis, plants have the ability to convert air and water into their own food. They accomplish this by capturing carbon dioxide from the air and drawing water from the soil, then breaking down these elements into their molecular components.
Plants extract hydrogen and oxygen from water, and carbon and oxygen from the air, which they utilize to create sugars like glucose. Additionally, they release surplus oxygen into the air as a gas during this process. Consequently, plants help to cleanse the atmosphere of excess carbon dioxide and enrich it with the essential oxygen required for respiration.
Photosynthesis is the process through which plant proteins generate sugars by absorbing adequate sunlight. Conversely, during the absence of light at night, plants uptake oxygen and discharge carbon dioxide, much like humans and animals.
Besides carbon dioxide, plants possess the ability to assimilate volatile organic compounds from the atmosphere, including harmful ones like formaldehyde, carbon monoxide, benzene, and methane.
These toxic compounds are emitted into the air from plastic decomposition, cleaning agents, air fresheners, tobacco smoke, and automobile exhausts that infiltrate homes.
Certain plants amass volatile organic compounds in their leaves, while others utilize them for their own needs, and some even excrete them into the soil through their roots to nourish soil bacteria and fungi.
Therefore, it seems reasonable to assume that indoor potted plants contribute to cleaner and more breathable air. However, in reality, the matter is not as straightforward as it appears.
Can plants saturate indoor air with oxygen?
In short, indoor plants do produce oxygen during their growth, which involves the development of leaves and roots. However, the amount of oxygen generated by plants is insufficient for human needs.
The rate of growth differs among plant species, with an average indoor plant gaining approximately 0.2 grams of weight per day. Botanist Marco Thorne estimated that the average plant produces a mere 30 milliliters of oxygen per day.
Comparatively, an adult inhales and exhales 7-8 liters of air every minute, containing around 20% oxygen, of which humans only absorb 5%. Therefore, an individual requires approximately 550 liters of pure oxygen per day.
Despite the importance of indoor plants, their contribution to oxygen saturation in the air is relatively small. Moreover, plants also breathe like humans at night, further decreasing their oxygen-producing potential.
Can plants clean indoor air from volatile organic compounds?
Once again, the answer is affirmative, but the benefits of indoor plants for purifying air may not be significant for residents living in a typical urban apartment.
In 1989, NASA sought an inexpensive and eco-friendly way to improve air quality in space stations and found that green plants could potentially serve this purpose. To investigate this further, NASA researchers conducted an experiment where they placed 12 different plant species in sealed chambers of 1 cubic meter volume, injected formaldehyde, benzene, and trichloroethane into the chambers, and measured the remaining volatile organic compounds after a day. They discovered that the plants removed between 10% to 70% of the harmful substances during this time.
Nine plants were identified by the scientists as the most effective in this task: bamboo palm, Schefflera, garden chrysanthemum, Dracaena marginata, creeping ivy, nephrolepis, philodendron, peace lily, and azalea. Based on this study, many people have inferred that indoor plants can eliminate volatile organic compounds from the air.
However, in 2020, two US Department of Civil, Architectural, and Environmental Engineering employees began to question the effectiveness of indoor plants in purifying air. They pointed out that the initial experiment had been conducted in a sealed 1 cubic meter chamber, which was not representative of a typical urban room measuring 38 square meters with 100 cubic meters of air that is replenished every hour due to windows and a functioning ventilation system.
These engineers analyzed data from 196 experiments involving potted plants, while considering factors such as the size of residential rooms, the rate of air exchange between the room and the outside, and the duration of plant presence in the room.
The outcome of their analysis was that potted plants do not improve air quality indoors – as reported in the Journal of Exposure and Environmental Epidemiology.
Upon further scrutiny, it was discovered that to replicate the results obtained by NASA, it would require placing 10 plants per square meter in a typical urban apartment, or even up to 380 plants in an apartment with high air exchange rates. This is clearly an impractical number of plants.
How indoor plants really affect people’s health
While houseplants are not expected to serve as a substitute for air filters, this does not imply that they are only useful for decorating interiors. Plants have the ability to enhance our mood, and some researchers are optimistic that potted greenery could assist in combating the COVID-19 pandemic.
Plants make studying more enjoyable
As an example, students from Taiwan who attended classes in rooms where 6% of the floor space was adorned with green plants experienced a greater sense of ease and displayed more amiable behavior towards one another compared to those in a classroom devoid of plants.
Plants maintain psychological well-being during self-isolation
Italian psychologists conducted a survey of nearly 4,000 compatriots in 2020 and discovered that individuals who owned more plants in their homes experienced reduced levels of anger, anxiety, fear, and sleep difficulties during self-isolation. Nevertheless, these findings are still preliminary and require further validation.
Should these results be corroborated, it may be possible to determine the requisite number of plants required to promote mental well-being. This could potentially make green spaces in hospitals and nursing homes an effective approach for safeguarding the psychological health of elderly individuals and those suffering from illnesses.
Plants help maintain optimal room humidity
Numerous studies have demonstrated that plants are capable of adding moisture to excessively dry air while absorbing excess moisture from overly humid air. The humidity levels maintained by plants can help prevent mold proliferation and aid in the evaporation of small water droplets that viruses can be transmitted through when coughing or sneezing.
Certain scientists are even optimistic that live humidifiers, such as plants, could potentially reduce the transmission of the coronavirus. If forthcoming research indicates that individuals who own plants are less prone to contracting COVID-19, this would represent a notable benefit for indoor gardening.
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