Gas treating apparatus

A VOC concentrating apparatus includes a honeycomb rotor. In order to lower concentration at an exit of adsorption and at the same time to be able to regulate the amount of air flow introduced into a desorbing zone, independently from the amount of cooling air, there are disposed a cooling zone, desorbing zone and an adsorbing zone in the honeycomb rotor. The honeycomb rotor rotates and thus passes through the zones one after another. After gas to be treated has passed through the adsorbing zone, concentration of VOC in the gas is measured on the exit side by a concentration detector. The cooling air is divided by a damper for regulating the amount of air flow, after having entered the cooling zone, and a part thereof enters the desorbing zone through a heater. Further air coming out therefrom is heated again by a heater to enter the desorbing zone and concentrated gas is removed.