Traditionally, contamination control in SEMs has focused on pump oils, finger prints, dirty specimens, and good vacuum practice in manufacturing. Now, the use of dry pumps at all stages of the vacuum system of new FE SEMs, and the use of better vacuum practices on the part on users and manufacturers have made environmental hydrocarbons, the hydrocarbon background contamination of our world, a significant source of the remaining hydrocarbons in electron microscope vacuum systems. These environment sources of hydrocarbons (HC) cause a loss of resolution and contrast in imaging at the highest levels of magnification.