When a gas is introduced into the chamber of an environmental or low-vacuum SEM, the gas molecules cause the beam to scatter. The higher the chamber pressure or the longer the working distance, the more the electron beam will scatter. This scattering generates X-rays away from the original beam spot, producing errors in the analysis.

Electron Flight Simulator, version E lets you vary the chamber pressure, gas type, accelerating voltage, and working distance to correct for this scattering.