Models OZ-20, OZ-30 Portable Ozone Meters DKK-TOA offer two versions of portable ozone meter. The Model OZ-20 is for Ozone measurement in water and the Model OZ-30 is for measurement of ozone in a gas phase samples. These units use a polarographic membrane type technique so that no reagents are required for analysis. Ozone is used primarily for disinfection purposes and the concentration needs to monitored since it is considered a hazardous material. These meters can be field operated. The LCD display shows all appropriate parameters and an easy to follow calibration procedure .