ISO 8672:1993

Air quality — Determination of the number concentration of airborne inorganic fibres by phase contrast optical microscopy — Membrane filter method

The principle of the method specified is collecting a sample by drawing a measured quantity of air through a membrane filter by means of a battery-powered sampling pump, transforming the filter from an opaque membrane into a homogeneous optically transparent specimen, sizing and counting the fibres using a phase contrast microscope. The results are expressed as fibres per cubic centimetre of air, calculated from the number of fibres on the filter and the measured volume of air sampled. Limitations of the method are stated.