Air Purification Capability of Charcoal and Its Evaluation

Charcoal has received much attention recently because of the various kinds of effective functions it can be put to. Especially, its deodorizing capability indoors has been well recognized. However, an evaluation method for this capability has not been established. It is necessary to devise a suitable method and introduce this capability to the general public using an index value. They can then understand the capability easily by the value and use it positively. In this study, an evaluation method is proposed, wherein the deodorizing capability of charcoal is evaluated in an experimental chamber using a tin oxide gas sensor, which outputs a signal according to the concentration of an air‐polluting chemical. The sensor output increases as the concentration of the chemical increases. The index value (P_a) indicating the capability can be represented using the sensor output characteristic to the chemical, using the peak value (h) and the half‐value width (t_w); P_a = h/t_w × 100. The peak value here means the voltage from offset level to the peak value of the output. Four kinds of charcoals were examined. Especially, charcoal from Japanese cedar and oak were investigated. The results show that both samples give almost same value (P_a = ∼10). Cedar charcoal is cheaper and the heat energy required is also lower than for oak charcoal. This is good for cedar charcoal. It is considered that by installing charcoal in an indoor environment the air quality can be improved and people can have a safe and comfortable life. Charcoal has therefore the capability to remediate indoor air pollution. © 2010 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.