The AQF31 model, when used as an accessory with the QFA31 model, is designed for outdoor use, and in ventilation and air conditioning plants requiring high accuracy measurement within short response times. Its humidity range covers the the entire range of 0-100% relative humidity, while its temperature range spans from -40°C to 70 °C (-40°F-158°F). The AQF has an IP65 protection class rating.