Houseplants are a popular choice for enhancing indoor environments, valued for their aesthetic qualities and their perceived ability to purify the air. As homes become more sealed for energy efficiency, the desire to find natural ways to filter indoor air quality has made the houseplant a fixture in modern interior design. Understanding how these organisms interact with the atmosphere reveals their dual role in gas exchange and toxin absorption.
Understanding the Oxygen Cycle: Photosynthesis and Respiration
Plants engage in two continuous biological processes involving atmospheric gases: photosynthesis and respiration. During the day, photosynthesis is the dominant process. The plant takes in carbon dioxide (CO2) and water to produce energy, releasing oxygen (O2) as a byproduct through tiny pores called stomata. This daytime oxygen production gives plants their reputation as oxygen generators.
Cellular respiration occurs constantly, day and night, as the plant breaks down stored sugars for growth and metabolic functions. Respiration consumes oxygen and releases carbon dioxide. For most plants, daytime photosynthesis far outweighs nighttime respiration, resulting in a net positive oxygen output over a 24-hour cycle. Certain succulents use Crassulacean Acid Metabolism (CAM) to absorb CO2 primarily at night, which can result in a small release of oxygen overnight.
Top Indoor Plants Recommended for Air Quality
The selection of houseplants for air purification often focuses on species that thrive indoors with minimal light and are known for their filtering capabilities.
- Snake Plant (Sansevieria trifasciata): Also known as Mother-in-Law’s Tongue, this resilient plant tolerates low light. It is favored for bedrooms because it uses CAM photosynthesis to exchange gases after dark.
- Peace Lily (Spathiphyllum): Recognized for its elegant white flowers and effectiveness in filtering various air pollutants. It performs best in medium to low-light areas but requires consistently moist soil.
- Golden Pothos (Epipremnum aureum): This adaptable trailing vine, often called Devil’s Ivy, is extremely easy to grow. Its efficiency in removing common household chemicals makes it ideal for beginners.
- Boston Fern (Nephrolepis exaltata): A strong performer for those seeking a plant that also adds humidity to dry indoor air.
- Spider Plant (Chlorophytum comosum): A classic, forgiving houseplant known for its ability to filter formaldehyde.
Beyond Oxygen: The Role of Plants in Removing VOCs
The ability of plants to clean indoor air extends far beyond the simple exchange of CO2 and O2, encompassing the removal of Volatile Organic Compounds (VOCs). These compounds are carbon-based chemicals that easily evaporate at room temperature, released from common household items like paints, furniture, and cleaning products. Formaldehyde, benzene, and trichloroethylene are examples of VOCs that can accumulate in tightly sealed indoor environments.
The foundational research was the NASA Clean Air Study in 1989, which tested common houseplants in sealed laboratory chambers. This study introduced the concept of phytoremediation, demonstrating that plants absorb these toxins through their leaves, which then travel to the root zone. Crucially, the microorganisms living in the plant’s soil play a significant role by breaking down the absorbed VOCs into harmless substances.
Caring for Your Air-Purifying Plants
To maximize the air-cleaning potential of indoor plants, proper care and placement are important. The effectiveness of a plant’s filtering process is directly related to its health and growth rate. Most air-purifying plants prefer bright, indirect light, which fuels photosynthesis and maintains a robust metabolism.
Correct watering is equally important. Overwatering can lead to root rot and foster mold growth in the soil, negating air-cleaning benefits. Allowing the top layer of soil to dry out slightly between waterings is a good general practice. For a measurable impact on air quality, the original NASA researcher suggested placing at least one good-sized plant (in a six-to-eight-inch pot) for every 100 square feet of interior space.