National Oceanic and Atmospheric Administration (NOAA), Earth System Research Laboratory (ESRL)

The Pollak CNC was a manual unit which used water vapor to produce counts in a Condensation Nuclei Counter (CNC). When the Pollak CNC was in operation at MLO, the TSI instrument (Thermo Systems Incorporated) was compared to the Pollak CNC once a day. The TSI unit is a continuous-expansion CNC (see CMDL Aerosols) by which particle number concentration is determined when particles are exposed the to a high super saturation of butanol vapor. This causes the particles to grow to a size where they can be detected optically and counted. The instruments in use have lower particle-size detection limits of 10-20 nm diameter.

CMDL's General Operations Manual for our Aerosol Systems will describe precisely how these measurements took place. The project involved the Pollak Condensation Nuclei Counter, which measured daily at Mauna Loa Observatory.

This project is no longer active.