Self-Acting Fire Escape Dog Door

Many dog owners leave their pets shut up in the house when they are out. There’s nothing wrong with this, and sometimes it’s necessary for the safety of the dog; in other cases, the dog is guarding the house.

However, the dog is at risk if a house fire occurs while the premises are unattended – the dog has no means of escape. A “dog flap” large enough to accommodate larger breeds will also allow a burglar to enter ….

So, what is needed is a Self-Acting Fire Escape Dog Door. The whole system is integrated into the door, allowing it to be quickly and simply retrofitted to existing premises with no architectural modifications beyond the lock strike and the hinges; but possibly, the unit could be supplied in uPVC complete with frame.

Externally, the door is indistinguishable from a standard door. The upper portion may be glazed or plain at the choice of the purchaser -–a number of styles would be offered. The lower third of the door contains a square (apparently decorative) panel, about 600 mm a side. Such panels are commonplace on many doors and would not attract attention; a moulding conceals the seam and weatherseal. The weather seal consists of an outer wiping silicone rubber seal, and an inner single-use 50 micron polythene or polypropylene membrane, which tears away as the panel is ejected.

The panel is retained by a set of vertical sliding latches, connected to pneumatic actuators; these would be rotary, and release the panel by tuning leadscrews which disengage the latches, allowing pre-tensioned springs to eject the panel outwards. Power for the actuators comes from a pair of CO2 cartridges in a casing within the door structure. The complete actuator system (pressure reservoirs, actuators) is duplicated to provide reliable operation.

Positioned at the top inner side of the door is a smoke/heat detection system. This would be a rate-of-rise or fixed-point detector, rather than an ionisation or optical detector, since the probably location of the door is a kitchen or utility room where smoke and/or steam may intermittently be present, leading to false alarms. Power is provided by a 9V lithium thionyl chloride battery, and a backup alkaline battery provides the power to operate the gas release valves. Battery life for the detector battery should be minimum one year.

A manual mechanical override system is provided for human actuation.

Since the door is cosmetically indistinguishable from a conventional door, and the locking mechanism should have at least the same rating as the perimeter locking system, fitting an escape door like this does not reduce physical security. However, the system can be defeated by dropping a smoke bomb through a letterbox or window which would cause the panel to release. Since this will also release the dog (who will no doubt be irritated and/or frightened by the smoke) this may not be as much of a problem as one might first envisage.

Extra: The door is equipped with an alarm to indicate it has activated. The frequency and volume of the alarm should be chosen so as to be uncomfortable to canines, so as to encourage them to vacate the room. If the alarm runs continuously the dog will retreat from the noise (which will be coming from the direction of its escape route), the sounder can either be a slave unit on the other side of the room, or cycled on a 1:4 duty cycle every 20 seconds to allow the dog to exit between bursts.