Vallox 90K 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 9 Safety switch 10 Internal humidity sensor Internal carbon dioxide sensor 11 Control panel 12 Carbon dioxide sensor (optional) 13 Humidity sensor (optional) 14 VOC sensor (optional) 15 Cooker hood 16 Damper button 17 Fan speed adjustment