Back to business after a brief vacation in Costa Rica…

This is the 5th post in a series about fire doors and the results of a recent (unscientific) survey.

Rule #2 – A fire door must be SELF-LATCHING.

This means that when a fire door closes, it latches, typically with either a lockset/latchset or fire exit hardware. The reason for the latching requirement is to keep the door closed despite pressures that may be present during a fire.  If the latch is disabled, the door may open and allow the spread of smoke and flames.

When a latch on a fire door is deactivated or removed, it’s usually for one of two reasons.  1) The locking function of the door makes it inconvenient for building occupants when the door constantly closes and locks, or 2) The latching mechanism has become defective.  Both of these issues can be resolved fairly easily, so if you see a fire door that doesn’t latch, bring it to the attention of the building maintenance department.

I am working on a new web site regarding the requirements for fire doors and fire door assembly inspection, and there is a page on that site describing latching requirements.  It also lists additional lock-related requirements of NFPA 80, and includes some photos of non-compliant methods for holding a latch retracted (click here to check it out).

One term that I should explain for any non-door-people reading this, is the term “dogging.”  This term is related to panic hardware, and it refers to a means of holding the latch retracted to create a push/pull (non-latching function).  Many aluminum storefront doors are unlocked in this way – the panic hardware is dogged, holding the latch retracted, and then the door pull can be used to open the door.  Mechanical dogging is accomplished with a key or an allen wrench, and this feature is not present on fire exit hardware.  If the dogging function is desired for fire exit hardware, electric latch retraction or electric dogging can be provided, as long as the latch is released upon actuation of the fire alarm, allowing it to project and latch the door.

People often ask me where the term “dogging” comes from.  I’ve heard theories about it originating from a sailing term, or “dogging the hatch,” but today I found an explanation that sounds even more plausible:

“In engineering, a dog is a tool that prevents movement or imparts movement by offering physical obstruction or engagement of some kind. It may hold another object in place by blocking it, clamping it, or otherwise obstructing its movement. Or it may couple various parts together so that they move in unison – the primary example of this being a flexible drive to mate two shafts in order to transmit torque. This word usage is a metaphor derived from the idea of a dog (animal) biting and holding on.” Source: Wikipedia

If you have a theory of your own about the origination of the term “dogging,” share it with the rest of us by leaving a comment!

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