Abstract: A particulate matter measuring apparatus including an inlet for introducing air, a cyclone means fluidly connected to the inlet, the cyclone means adapted to remove particles of a predetermined size from the air, a particle detector to detect particulate matter in the air and a pump to move the air from the inlet, through the cyclone means and through the particle detector, wherein the particle detector has a laser diode to shine laser light through the air and a detector angled at between 115° to 140° relative to the direction of the laser light to detect an amount of laser light scattered by particulate matter in the air.