Condensation particle counters for ultrafine and nanoparticle measurements. Condensation particle counters (CPCs) are devices used to measure the number concentration of airborne particles in a sample of air. CPCs operate by using a supersaturated vapor to grow particles to a size that can be easily detected and counted.

The basic operation of a condensation particle counter involves drawing a sample of air through a saturator, which is a region filled with a vapor that is supersaturated with a condensable gas, typically butanol. The supersaturation causes the condensable gas to condense onto any particles present in the air sample, forming droplets around the particles.

The droplets then grow by further condensation as they move through a region with a lower supersaturation, called the growth region. Finally, the particles are counted by a detector that detects the light scattered by the droplets.

One advantage of condensation particle counters is their high sensitivity and low detection limit. Condensation particle counters can detect particles as small as a few nanometers in diameter and can count particles at concentrations as low as a few particles per cubic centimeter. Condensation particle counters are commonly used in a variety of applications, including air quality monitoring, aerosol research, and clean room monitoring.

They are particularly useful for measuring the concentration of ultrafine particles, which can be difficult to measure using other techniques. One limitation of condensation particle counters is that they can only measure the number concentration of particles, and not their size or composition. However, condensation particle counters can be used in conjunction with other instruments, such as scanning mobility particle sizers (SMPS), to provide information on the size distribution of particles in a sample.