A safety barrier is a component which prevents access to a dangerous area. In an industrial system, it is a guard such as a fence or window, designed to keep the operator away from moving parts or other hazards. It is commonly used to mitigate risk

Risk

Risk is the potential that a chosen action or activity will lead to a loss . The notion implies that a choice having an influence on the outcome exists . Potential losses themselves may also be called "risks"...

 in the Hazard-Barrier-Target model, as studied in safety science.

Hard barriers are be fixed or removable guards which prevent entry. Soft barriers are devices such as light curtain

Light curtain

Light curtains are opto-electronic devices that are used to safeguard personnel in the vicinity of moving machinery with the potential to cause harm such as presses, winders and palletisers. Light curtains can be used as an alternative to mechanical barriers and other forms of traditional machine...

s which detect the presence of a foreign body and are tied into the control circuit to stop the machine.