Scaffolding has been put up on my council property blocking all access to upstairs windows they are going to do guttering and facia boards but unable to get air upstairs and concerned no fire escape if a fire broke out downstairs is this safe and how long is reasonable to have this up for 

Insufficient information you would need to provide a full details of the type, layout and preferable the premises need a professional fire safety survey to give you a full answer to your question.