Zehnder EVO 2 with Enthalpy Exchanger CA155CM_SPARES you will be equipped for you will be equipped for the most important measurements involving domestic heating systems: the testo 300 flue gas analyzer is supplied with O2 and CO sensor up to 4 Suitable for use with the Zehnder ComfoTube Flat 51 semi rigid ductwork and comes complete with award winning RapidLock® connections to quickly form an air tight and robust seal by simply push fitting the semi rigid ductwork when combined with the o ring seals sold separately The unit’s efficient motor and constant airflow technology ensure a balanced flow rate while minimizing energy consumption · Passivhaus Institute Certification