A more modern type of particle counter is the light scattering APC. As with the light blockage method, particles produce a measurable interference in the transmission of light through the sample in the light scattering cell. However, instead of simple white light, this method employs a laser. The highly focused light emitted is interrupted by a particle, producing a scattering effect. The increase in energy across the sampling area is measured with this type of particle counter, just the opposite of the light blockage method (Figure 2). There are very few laser sensor OEMs despite the variety of instruments available on the market. Many have been repackaged and private-branded.