A method and system for monitoring using a sub-slab sensor assembly for a building having a slab includes a housing, a first air quality sensor coupled to the housing and generating a first air quality signal for air above the slab, a second air quality sensor coupled to the housing and generating a second air quality signal for air below the slab and a pressure sensor coupled to the housing. The pressure sensor generates a pressure signal corresponding to the pressure below the slab. A position sensor generates a position signal corresponding to a location of the sensor. A network interface communicates the first air quality signal, the second air quality signal or the pressure signal, or warning signals corresponding thereto and the position signal to a network.