Aitken nuclei counter A device invented by John Aitken that is used to estimate the concentration of particles with radii of more than 0.001 μm in a sample of air. Air is made to expand in a chamber. This causes it to cool and water vapour in it condenses on to particles, forming a mist whose opacity allows estimation of the number of particles present. See also Aitken nucleus.

Aitken nuclei counter Device for the estimation of the concentration of particles with radii of more than 0.001 μm in a sample of air. Air is made to expand in a chamber: this causes it to cool. Water vapour in it condenses on to particles, forming a mist whose opacity allows estimation of the number of particles present. See also AITKEN NUCLEUS.