What we call "EEG" data is the electrical scalp signals from each channel. It contains a mixture of pure brain data, muscle artefacts, ocular artefacts (the eyes are large dipoles and when they move it generates large electrical impulses at a lot of locations), motion artefacts (sensors moving over the skin or being bumped), electrostatic signals (eg from someone walking past or holding their hand near a sensor - especially if they are electrically charged) and electrical mains pickup from power and lighting in the building, PC power supplies and cases, etc. It's all mixed into the signal we record. We don't do anything to separate it out of the exported files. However, there are many tools that can separate these things - such as in EEGLab (for example, Independent Components Analysis, Cleanline function etc).