1.LCD display CO2 in room air 2.temp&RH option, RS485 ... (default)0~20,000ppm, programmable selection0~50,000ppmtCO2 setting & Display resolution1ppmTemperature measuring/ setting range0~50°C(32~122°F)/ 5 ... selectable4) Built-in pump type for some special applications5) LCD display detecting both CO2 level and temperature, also relative humidity ( ... a relay output to control a fan. air control unit