Indoor air monitoring using newly developed portable formaldehyde monitoring device

Abstract

We have developed a portable device for formaldehyde monitoring, and have carried out indoor air monitoring in several houses. The absorbance difference of the developed sensor element was measured at regular intervals in the monitoring device and converted into the formaldehyde concentration. This was possible because the rutidine derivative that was formed as a yellow product of the reaction between β-diketone and formaldehyde was stable in the sensor element. The device contained an LED as a light source and photodiodes as photo-detectors. It was sufficiently small (10 cm × 10 cm × 4 cm) to be installed at a desired location in the house. In addition, the device was able to monitor a closed area without a convection flow, because it did not use a pump for air sampling. The detection limit was 5 ppb x hour, and we estimated it took about 1 hour to detect a formaldehyde concentration of 94%.
The developed sensor device was small and easy to use and we successfully carried out hourly formaldehyde monitoring using our monitoring device under several indoor conditions. We found that a high formaldehyde concentration could be measured in a room containing furniture and clothes. We also found that, although the formaldehyde concentration decreased rapidly when ventilation was provided, it recovered rapidly in several hours when we stopped ventilating the room.