During the QUEST 1 campaign we measured the aerosol flux by the eddy covariance method using a condensation particles counter (CPC) and an optical particles counter (OPC) from the 25 m tower at the coastal research station Mace Head at the Irish west coast.This gave us the aerosol flux in the 10 to 100 nm diameter range (the difference between the CPC and the OPC aerosol flux) and a size resolved flux from 100 nm up to a few micrometer (above which the majority of the aerosol was lost to the sampling line).A heating unit enabled us to separate the flux of non-volatile aerosol particles,in practise sea salt particles,by heating the air up to 300 o C.Thus,the difference between the unheated aerosol flux and the heated aerosol flux is most likely semi volatile organic carbon.