In our homes, greenery is often seen as a natural air purifier. Not only do plants add a vibrant touch of green to our living spaces, but they are also believed to absorb harmful gases, release oxygen, and improve indoor air quality. However, can these green companions really purify the air as effectively as we think?

How Plants Breathe

During the day, through photosynthesis, plants absorb carbon dioxide and release oxygen. This process involves water absorption and transpiration, which helps plants take in minerals and nutrients. At night, plants consume oxygen and release carbon dioxide through respiration. This creates a remarkable balance in nature.

How Plants Purify the Air

Plants have tiny pores on the surface of their leaves that can absorb harmful substances in the air, such as formaldehyde, benzene, and ammonia. These substances are converted into nutrients or harmless compounds within the plant. A NASA study in 1989 supported this, showing that houseplants could help clean the air. However, the study was limited to one cubic meter of confined space and concluded that, in a single day, plants could remove up to 70% of harmful gases.

How effective are plants at actually purifying the air?

Burning wood, coal, and gasoline produces harmful chemicals released into the atmosphere, known collectively as volatile organic compounds (VOCs). In homes, the use of paints, detergents, furniture, and other products can release these chemicals. NASA's research was conducted in small, sealed chambers, which are very different from the actual indoor environments we live in.

A paper published by researchers found that the average capacity of a plant to purify air is about 0.023 cubic meters per hour, compared to 100 cubic meters per hour for an average air purifier. This means that hundreds of plants would be needed to match the air purification capacity of a single air purifier.

To be more precise, in a 140-square-meter room, approximately 680 potted plants would be needed to replace the air as effectively as opening a window. This equates to more than 5 potted plants per square meter. As a result, plants remove harmful gases (VOCs) indoors at a much slower rate compared to how air circulates in buildings.

Therefore, using a building ventilation system or an air purifier to dilute VOCs is much faster than relying on plants to absorb VOCs from the air.

To effectively improve indoor air quality, it's essential to consider ventilation, the selection of interior decoration materials, and our daily living habits.

Although planting greenery doesn't directly purify the air, it offers other benefits

Being in a space filled with plants feels distinctly different from being in one without, even if they don't purify the air. Certain plants can create a more relaxing and invigorating atmosphere. Surveys have indicated that plants can positively influence people's physical and mental health, with the effects becoming more pronounced as the quantity and variety of plants increase.

In modern times, as research into the therapeutic effects of interacting with plants deepens, "horticultural therapy" has emerged. Horticultural therapy encompasses the social, emotional, physical, cognitive, and spiritual benefits that individuals can experience through gardening activities such as planting flowers and fruits, creating dried flower crafts, and engaging in therapeutic landscaping. Numerous studies have now confirmed that living alongside plants can effectively reduce physical and mental stress and enhance emotional well-being.