An ASTM Smoke Pump, or 'spot pump', is an instrument for evaluating the dark particle concentration of a smoke. It is very widely used (2014) by heating engineers to assess emissions, most commonly from fuel-burning appliances such as a wood stoves or oil boilers. It consists of a cylinder of precise size down which a close-fitting piston is pulled, sucking a sample of the smoke through a small nozzle against a filter paper (equivalent to Whatman No2 paper) so that a 'spot' is formed on the paper, the darkness of which can be compared with a standard chart to indicate the concentration of smoke.