From a botanical perspective, all plants engage in processes that can alter the composition of the air around them. The primary mechanism is photosynthesis, where plants absorb carbon dioxide (CO2) and release oxygen (O2). While this certainly "refreshes" air quality by increasing oxygen levels, it does not constitute "purification" in the context of removing toxic volatile organic compounds (VOCs). For that, we must look to a secondary process: phytoremediation. This is a plant's ability to absorb, through its leaves and roots, certain gaseous and particulate pollutants from the air, which are then broken down by metabolic processes or supported by microorganisms in the soil. Boston Ferns (Nephrolepis exaltata) are often cited as being particularly effective at this form of botanical filtration.
The widespread belief that Boston Ferns are superior air purifiers stems directly from a landmark study conducted by NASA in 1989. The research aimed to find efficient ways to purify air in sealed space stations. The study tested several common houseplants for their ability to remove key VOCs like formaldehyde, xylene, and benzene from a closed chamber. The results indicated that the Boston Fern was exceptionally proficient, particularly at removing formaldehyde. It is crucial to understand the conditions of this study: it was a controlled, laboratory environment with high concentrations of pollutants and constant, high-intensity light—conditions that are difficult to replicate in a typical home or office setting.
While the NASA study provides a strong scientific basis for the plant's capabilities, translating these results to a real-world setting presents significant challenges. The air purification effect observed in a sealed chamber is dramatically diluted in a normal room with constant air exchange from doors, windows, and HVAC systems. To have a measurable impact on indoor air quality comparable to the study, one would likely need a very large number of plants—potentially 10-20 per square meter of floor space. Therefore, while a Boston Fern is actively engaging in phytoremediation, the scale of its impact in a typical living space is vastly smaller than often perceived. It is a contributor to better air, not a comprehensive solution.
Beyond the debated removal of VOCs, Boston Ferns contribute to a healthier indoor environment in other, more tangible botanical ways. They are excellent natural humidifiers. Through a process called transpiration, they release moisture vapor into the air, which can alleviate the dryness caused by heating and air conditioning systems. This increased humidity can help reduce airborne dust particles and alleviate respiratory irritation. Furthermore, like all plants, they can have a positive psychological impact, which, while not a physical purification process, contributes significantly to human well-being in an indoor setting.
