Hi was wondering if someone can help me. We moved onto a property 10 years ago. The property leads onto a enclosed  back yard.  Our next door Neighbour only has a roof terrace so only one entrance into the property. The owners agreed a back door would be installed in our neighbour property that would lead into our yard. This door would be used in the event of a fire. It is not a communal property. New tenants have moved in and leave the door open for ventilation. I have expressed my concerns with there letting agent that this is a safety risk for me as I have small children who could enter there property. The letting agent says they can open the door for ventilation as there kitchen window doesn't open wide. (It does the previous tenant would climb in it when drunk and forgot her keys). There do I stand, if it's a fire exit I'm sure it can't be used for anything else but an exit. And its it's for ventilation then legally I can block it as it's not a fire exit? 

A fire exit could be use for any purposes as long it is available in the event of a fire, if required to escape.

This is not a fire safety matter it is a legal matter and it would depend on your terms and condition of you tenancy agreement so I would suggest you seek tthe advice of a lawyer.