1. to investigate the influence of various factors on the concentration of markers in EB(C); parameters on a subject level (e.g. breathing pattern, nose clip, inspiratory filter, saliva contamination, physical exertion), on an apparatus level (cleaning procedures, temperature of the condenser tube, environmental conditions, buffer bags), and on a measurement/analysis level (sampling time, storage time, storage temperature, protein inhibitor or bovine serum albumine) can be discriminated.