Have you ever walked past a commercial building and wondered how those large, horizontal metal bars on the doors actually work? More importantly, if their primary job is to let people out quickly during an emergency, how do you keep unwanted visitors in?

You have likely seen them thousands of times in schools, hospitals, theaters, and office buildings. They are the horizontal metal bars running across the middle of heavy commercial doors. Known as panic bars, crash bars, or door push bars, these devices serve a critical life-saving function: allowing people to exit a building quickly during an emergency without fumbling for a lock or handle.

Have you ever walked past a commercial building and wondered how those large, horizontal metal bars on the doors actually work? More importantly, if their primary job is to let people out quickly during an emergency, how do you keep unwanted visitors in?

What Is the UL 305 Standard?The UL 305 standard, issued by Underwriters Laboratories (UL), serves as the leading U.S. safety benchmark for panic hardware—also known as panic exit devices or fire exit hardware. These devices are installed on doors in public and commercial buildings to facilitate rapi