Doorstops are pretty convenient for holding doors open.
Fig. 1: A doorstop. Or a wedge of cheese. OR PERHAPS BOTH??
But sometimes, propping open a door is FORBIDDEN due to fire regulations—the door might need to be closed in order to slow the spread of fire (Fig. 2).
Although there exist magnetic doorstops that connect to the fire alarm, it’s very likely that the door that you want to prop open isn’t set up this way. Read on for the solution!
Fig. 2: Unfortunately, this door needs to be able to close in case of fire (left), so the doorstop at right is forbidden.
A new, futuristic type of electrical doorstop can be set up to automatically detect fire alarm conditions and get out of the way (allowing the door to close).
The primary idea is that the “collapsable fire-safe doorstop” has a microphone, and if it detects the sound of the fire alarm, it will instantly flatten down to a wafer-thin state, allowing the door to swing closed (Figures 3 and 4).
Fig. 3: The collapsable fire-safe doorstop. A) Microphone and optical sensor, for detecting a fire alarm. B1/B2) Hinged doorstop pieces. The red hinge between B1 and B2 will open in case of fire. C1/C2) Flat end caps for the doorstop. D1/D2) A hook mechanism that normally keeps the doorstop in a wedge shape. It will unhook in order to let the doorstop flatten itself.
Fig. 4: The doorstop detects a fire (top) and disengages the hooks that keep it in a triangular shape (middle), finally flattening out to allow the door to pass over it (bottom).
The doorstop would need to be battery powered, but it could presumably run for months or years on just a single watch battery. The closure mechanism (the gray hooks in the figure) could presumably also be set up to require a tiny amount of electrical power in order to stay connected. In this way, the doorstop could automatically flatten when the battery ran out, which would prevent a dead battery from being a fire hazard.
Fig. 5: Do not open a door with a fire on the other side unless it gives the correct password.
PROS: Allows you to prop open that one annoying hallway door that everyone is opening and closing constantly.
CONS: It’s yet another electronic gizmo that requires battery monitoring and replacement.