Sub-micron particles, accounting for 97 per cent of all air-borne particles, can damage production yields [as in the semiconductor industry], affect product reliability [as in pharmaceuticals, food processing and manufacture of medical devices] and harm personnel directly. Met one of usa now offers air-borne particle counters that measure the number of particles in various size ranges and display the results as a cumulative count, differential count, or concentration. A range of models from the handheld model to trolley-mounted versions with built-in printers and accessories to measure differential pressure, air velocity, relative humidity and temperature are available. The counters have the flow-rate options of 0.1, 1 and 2 cfm, with sensitivities of 0.1, 0.3 or 0.5 micron.
