An air quality measurement apparatus, including a first air inlet providing a first air sample within a space; a device which is configured to draw an air sample through the first air inlet and over a sensor, wherein the sensor measures the first air sample for a first environmental condition; an air outlet for expelling the first air sample from said apparatus; a second air inlet providing a second air sample externally from the space to measure the first environmental condition whereby the second environmental condition is compared to the first environmental condition to provided data to a user regarding the difference.