|Do not inflate balloons near this building.|
This sign might be appropriate placed next to a sluice or some designer toilet bowl, but it was attached to a wall in an otherwise empty subterranean corridor.
Sounds fairly reasonable (subject to not washing the other hand as well), but why would anyone want to...
I suspect this is a euphemism similar to an American's request to 'use the bathroom' - that is to say that our US cousins do not actually want a room which contains a bath. Similarly, this sign has little to do with hand washing (other than it is recommended afterwards).
This pair of signs on the security man's desk are a little less obscure, and even provide a mobile phone number for continuity of service. Some people never go off duty.
The answer to the question above:
Tomorrow or whenever: Something else...