. . . . . Duct Mount Indoor Air Quality Sensor - The BA/AQS Series indoor air quality sensors are designed around a unique oxidizing element that varies in resistance with respect to the concentration of contaminant gases it contacts. The sensor is non-specific to any one gas. Instead, the output signal corresponds to the combined concentration of over 30 contaminant gases that are typically found in indoor environments. The BA/AQS Series is offered in wall- or duct-mount, with 0-5 VDC or 0-10 VDC outputs. As a part of an overall air quality control scheme, this sensor can be used to detect circumstances that require varying amounts of ventilation.. Bapi. Building Automation Products Inc. BA/AQS-D-10.