Vallox 101 MV R model in the figure. In the L model, the parts are mirrored. 1 Extract air fan 2 Supply air fan 3 Fine filter for supply air 4 Heat recovery cell 5 Bypass damper of the HR cell 6 Coarse filter for supply air 7 Coarse filter for extract air 8 Post-heating resistor (in the supply air duct) 9 Safety switch 10 Internal carbon dioxide and humidity sensor 11 Control panel 12 Carbon dioxide sensor (optional) 13 Humidity sensor (optional) 14 VOC sensor (optional) 15 Ceiling bushing for electric wires