The unit is designed to take fresh air from outside, filter the air, warm it (if fitted with a heater) and discharge it into the central hallway via a system of ducting. The unit is usually situated in a kitchen, airing cupboard or hallway, and is ducted to a central location. The interchangeable, multi-positional inlet/outlet spigots allow for quicker installation with only one external wall penetration.
The dwelling internal air discharge grille is usually installed at high level in a central location within the hallway, although discharging the air down the length of the hallway (away from the front door) should also prove acceptable.
Unit performance may be enhanced if an existing heat source can warm the discharged air eg, by locating the discharge grille above a radiator.