The Vent-Axia Lo-Carbon Tempra SELV P Single Room Heat Recovery Unit is available with Safety Extra Low Voltage, a constant trickle speed and with a pullcord or switch to boost airflow. The units are suitable for installation into external walls up to 318mm thick and all installations can be carried out from inside a building. To facilitate ease of maintenance and installation the Tempra\'s simple construction is not difficult to fit in the same location as an existing 100mm diameter fan and offers easy access to the heat exchanger for regular maintenance. Under the Building Regulations Document F, continuous running products such as the Lo Carbon Tempra are only required to move an amount of air as laid down in table 5.1a of Document F.