Exclusion Zone
An exclusion zone is to keep unwanted people away from an area, only allowing authorised users to enter the area. The main reason being that activities or features are especially hazardous and present a high risk of injury or harm to others.
It will be well signposted, protected and cordoned off to either keep people away from hazards created by some work activities, for example, cutting equipment, welding or from falling objects.
In addition, it might be an area that is not safe for entry, with everyone being kept outside of it until the hazard has been addressed and made safe.