A new Low Emission Atmospheric Metering Separator (LEAMS) was developed by Two-Phase Engineering and Research, Inc. and tested by Sandia National Laboratories in parallel with a cyclone separator at the Coso, California geothermal field. In order to determine the efficiency of the separator, a Jonas, Inc. Particle Monitor was installed in the exhaust from each separator to measure the mass flow rate and size distribution of water droplets exiting the separators. These tests provided semi-quantitative data on the improved separation provided by the LEAMS, as well as verification of the Jonas, Inc. Particle Monitor on geothermal steam systems. (C) 2004 CNR. Published by Elsevier Ltd. All rights reserved.