External rotor motors are usually contained within the width of the fan housing, thus saving the space normally occupied by a standard motor. They are located in the air stream, so temperature is limited, and are generally of protection class IP44, so the air needs to be clean and dry to avoid motor contamination.

Low cost speed control is possible by supply voltage variation, either by electronic (triac) method or by transformer.
As the scroll housings of single inlet fans are in fabricated steel it is possible to have detachable discharge flanges, which means that the fan can be mounted on its air inlet side.