This alarm system ensures that doors left open by mistake or intent won’t defeat the entire security system. This battery-powered alarm system can be field-set for door prop times ranging from one second to four minutes, with a 15-second default. After the time selected, a 100-decibel alarm alerts staff, then silences when the door is closed so there is no need to wait for a key-holder to arrive. The alarm is powered by a nine-volt battery and has a low-battery LED alert. The battery-powered option makes the alarm more economical to install and especially useful for retrofitting older facilities.