Why not use a platform lift during an evacuation? Or put it another why is it that normal enclosed lifts should not be used and why might it be acceptable to use to use a platform lift.

The danger with an enclosed lift is that if a fire breaks out the lift might lose power between floors in a lift shaft and the person in the lift will be very thoroughly trapped. But that is not usually the case with a simple platform lift. They will be lifting people not between floors but two levels in the same room not in an enclosed shaft. The duration of any sort of journey in the lift will be short:  a minute or two at most. We have a large meeting room and it is split on two levels. To get from one level to the next level where the fire exit is located you would have to use the platform lift unless we were to use an evac chair on the short set of stairs. Of course those stairs might be busy during an evacuation. The wheelchair user would have to be transferred to the evac chair which would also take time and require one or more persons to stay behind to help the wheel chair user. Using the platform lift is a better evacuation solution. Ideally the room would have been either built on one level or fitted with a ramp between levels but that was not what happened and we have to adapt to what we have.