Carl Prinzler

Carl Jacob Prinzler (June 6, 1870 – May 30, 1949) was an American engineer who invented the "panic bar" device for doors that allowed them to be opened from the inside despite being locked on the outside.

Prinzler would later recall that, as a naive young man with no real hardware experience, he once mistakenly sold a wash machine to a female customer in search of a butter churn.

[3] Prinzler, personally moved by the experience and loss of life, committed his thinking to developing door hardware that could remain locked from the outside while allowing safe and reliable emergency exit to people on the inside.

Working with his neighbor, Henry H. DuPont, an Indianapolis architect, the two men developed and were awarded a series of nine patents relating to new and improved exit door hardware.

All of the patent designs focused on a single lever bar (and related hardware) that would cause a locked door to pop open when simple interior pressure was exerted upon it.