Using ‘smart’ scent technology, deploy a number of scent delivery systems throughout the National Portrait Gallery.
The delivery system as a whole will be linked into a central processing unit, which will be monitoring the visitor numbers currently in the gallery.
At a pre-determined level, say 75% capacity, the scent will change from something like ‘Summer Meadow’ to ‘Rotting Shit’, thereby quickly emptying the gallery of visitors.
Once the numbers have dropped to another pre-determined level, around 25% capacity, the scent switches back to ‘Summer Meadow’, and the cycle starts again.