Detex Corp. offers a battery-powered door prop alarm system that guards against propping doors open. The EAX-300 door prop alarm 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. It is powered by a 9-volt battery and includes a low battery/LED alert.