BW GasAlertMicro5 Series Multi-Gas (1-5) Detectors simultaneously monitors up to five atmospheric hazards and a wide selection of toxic gases, you can choose two other variants of the BW GasAlertMicro5 Series, from a Photoionisation (PID) Detector or an Infrared (IR) Detector as well. The BW GasAlertMicro5 Series Multi-Gas (1-5) Detector monitors these gases such as PID VOCs, IR CO2, LEL, H2S, CO, O2, SO2, PH3, NH3, NO2, HCN, Cl2, ClO2 & O3.