The BESB box ventilator is used for bathroom, kitchen and clothes dryer exhaust as well as supply of combustion air/make-up air. In exhaust applications it is installed at the exhaust duct termination point where it ensures a negative pressure in the entire duct system - or in line. For optimal performance the fan speed can be controlled by a modulating pressure control (MEC 18).
In supply applications, it is installed at the air intake where it is controlled by an EBC 30 Modulating Pressure Control.
The exhaust fan is typically used in applications where there are central laundry facilities, multiple appliances on multiple floors, duct design issues (elbows, long runs etc.), code violations or where additional safety is required.