The main function of an Aerosol Photometer is to detect particulate matter in air or gas and register the concentrations encountered on the readout scales. The most common use of the Aerosol Photometer is the measurement of leaks in filter systems, or the measurement of the efficiency of filter systems. In establishing the integrity of a filter, it is necessary to use a challenge agent such as dioctyl phthalate (DOP) as a test aerosol. The challenge agent is required as there is not enough particulate matter in the ambient air to give a valid test. Detectable particle sizes range from approximately 0.1 micron to 100 microns. Particulates of various shapes and sizes tend to give an exponential reaction when passed through the optical chamber in this instrument. Theoretically, 100 one-micron particles or 10 ten-micron particles should give approximately the same reaction. Therefore, since the instrument reads concentrations of particulates regardless of size, shape or colour, many applications are possible providing a baseline of 100 micrograms per litre of 0.3 micron particles is established with the instrument. It is possible to take dust samples of the atmosphere and read the concentrations in relation to the base.

The Aerosol Photometers will directly measure the HEPA filter performance and are available in different models to suit a variety of requirements and applications. These instruments are totally self-contained, designed for ease of operation. Since they are portable and lightweight, they can be easily carried for on-site testing.