Hi, the need for restrictors will depend on the risks in the building and the design of the existing windows. I hospitals and similar we install restrictors on all patient or public accessible windows to prevent deliberate self harm or confused elderly people climbing out. There was a court decision this week where a private care home was fined £0.5m following a resident falling to her death from an unrestricted window. There are numerous types of restrictors available. I usually specify jaclocks. These are about £20 each and usually simple to fit to existing windows. If you have vulnerable people in your buildings I recommend following the HSE guidance on falls from windows in health and social care (Google). There are also several NHS safety alerts on this topic which can be found on the web. Just ensure you specify tamper proof ones or remove the keys once fitted and locked. Otherwise staff will override them in Hot weather; defeating the object!