Chemical Sensors for VOC Detection in Indoor Air: Focus on Formaldehyde

Abstract

This chapter will present a brief overview of the current sensors for VOC detection, in particular formaldehyde which has become one of the most problematic gases in indoor air. Many sensing technologies were exploited for this purpose but, in this chapter, we will focus on the impedimetric sensors. These sensors consist in a sensitive layer deposited on an insulating substrate fitted with a pair of electrodes. The detection is based on the change of conductivity of the sensitive layer due to surface interactions with the target gas provoking an electron transfer. This kind of sensor acts as a simple variable resistance and is often called chemiresistor. By principle, these sensors are simple, easy to integrate in classical electronics and cheap. Considering the nature of the sensitive coating, we can distinguish several families: metal oxide sensors, semiconductor polymer sensors or based on graphene. All 3 types of sensors will be described in this chapter.