Purification Effect of Areca Palm for Continuously Emitting Formaldehyde in a Real Office Environment

Plant air-purification effect to reduce formaldehyde in a real office environment was examined. A potted Areca palm (height: about 2m) was adopted as a subjective plant. Plant purification effect was evaluated using a tin oxide gas sensor and a commercial tool for formaldehyde measurement was also used. The effect became higher as the atmospheric formaldehyde concentration was higher. The concentration became lower as the plants were installed. The effect did not greatly increase when the number of the installed pots was increased to seven from four. Concentration of carbon dioxide increased up to 450ppm by placing the pots at night. It is, however, below the regulated value (1000ppm) of Japan building managing law. Light intensity in the room fluctuated periodically and the carbon dioxide concentration changed periodically according to the fluctuation of light intensity from outside. There was a negative correlation between their characteristics. When the characteristic of carbon dioxide concentration was shifted forward by 1 hour with respect to the light intensity characteristic, the maximum value of correlation coefficient was obtained to be about -0.9. An integration value of a sensor output curve with time after the setting of potted plants could be regarded as a measure of an exposure volume of the plants to formaldehyde. The exposure value was found to become smaller as the number of the plants increased. In the experiment, formaldehyde was emitted continuously and the atmospheric concentration was kept at about 0.3ppm and the value was decreased to about 0.1ppm by the potted plants. This is close to the regulated value of 0.08ppm by WHO.