Automatic Release Mechanisms.

[Tom Sutton]

I had  inquiry about Automatic Release Mechanisms (ARM), Dorgard in particular, did a little research and found out, providing they are category A then they can be used anywhere subject to a fire risk assessment. I had a little problem trying to find out what category Dorgard is, it appears to be cat C, but even that you can use them on staircase enclosures providing it is not a single staircase. Are ARM's used extensively?

[kurnal]

Yes all manner of ARMs are very widely used. Many people who install them are much less diligent than you Tom and have no awareness of BS7273-4. You will find Dorgards in many buildings with no automatic fire detection including local authority premises.  A nearby local comprehensive school has them on fire doors protecting a single staircase without any detection at all (manual break glass alarm system), a nearby private school has more of the same and the local council uses them in its main buildings to hold open the alternative exit doors from the  function rooms, again in a building with a cat M alarm system.

You can tell em but they can't see the problem!

[Dinnertime Dave]

There is also a Dorgard X

http://vserver.firecoltd.com/fire/dorgardx.aspx

Supposed to be category A when transmitter is hard wired into the fire alarm.

[AnthonyB]

Interesting the original DorGard which was a Cat C Product for years was re-classed as Cat B (now Standard) a year or two ago increasing the options for it's use.

Whilst recent years have seen them used in Cat M premises the phenomenon isn't new, I've seen traditional hard wired magnetic hold opens in similar situations.

Whilst it's important to use the right category device for the risk I'd still rather see a correctly fitted DorGard with a correct category of FD&W system (& proximity of sounders) than a door wedged with wooden wedges, extinguishers, etc (consigned half a dozen to wedge heaven today...)

[colin todd]

Tam, Dorgard is not Cat C.

[Tom Sutton]

I said it appears to be cat C because I could not find its category designation, except one that stated cat C but now AB says was re-classed as Cat B (now Standard) and DD with his link the Dorgard X is cat A, thanks to everybody for your help. When ARM's where first introduced there was a great distrust which has now completely evaporated, now they are using Dorgards in premises with only manual BGU's not much use for smoke control and fire come to that, how things have changed not to the good always.

[colin todd]

Tam, if there is no AFD, it is irrelevant as to what sort of door hold-open device you use.

[Tom Sutton]

Colin my point is if there is no AFD you shouldn't use any AMR's, which appears to be happening.

[kurnal]

Yes Tom you are right but it has been happening for a long time and as AB points out with magnets as well as other devices. Till BS7974-4 was published there was little definitive guidance on such devices, where they should be used and how they should interface with an alarm.  

Perhaps the  Dorgard and other similar acoustically triggered devices, by their simplicity and free availability, tended to be more likely purchased and installed by building users without regard to the provision of detection though.

For  the benefit of others reading this forum  Without automatic fire detection - ie smoke detectors either side of the door- such devices have only the smallest of benefits compared to a wedge. All things being equal the door should close when the fire alarm sounds - ie  its a wedge that removes itself - but until the fire is detected by a human and the alarm is operated there is no barrier to smoke and fire spread through the door so the open door provides no protection to the means of escape.

[Auntie LIn]

Is no-one thinking about where such devices are fitted?   If there's an overhead closer fitted then any hold open device should be fitted at the same level as the closer to stop the leaf distorting - anything fitted at the sole, be it wedge or Dorgard, has the potential to distort the leaf so that it doesn't fit the frame properly if and when it's closed.

[Mike Buckley]

Lin, don't tell them that you are destroying the fire door replacement industry!!

[Bruce89]

They are normally fitted to improve freedom of movement around the premises e.g. Care homesetc., obviously this freedom of movement isn't so important at night when the residents are tucked up in bed or no occupation I.e. Schools, and therefore if the doors are then shut as they should be then the warping of the door is not such an issue I.e. "Automatic fire door keep clear close at night" signage.

[colin todd]

Big Al, having detectors only immediately on each side of the door went out with old fashioned concepts like friendly and helpful enforcement.

[kurnal]

Thanks Colin my comments were aimed at the 100 or so casual users of the forum who are browsing at any time and who are more likely to just buy a Dorgard on eBay and screw it a door without thought.
Bearing this in mind I would be grateful if you could suggest a form of words to replace mine without  going into the nuances of BS7273-4?

[idlefire]

Big Al, having detectors only immediately on each side of the door went out with old fashioned concepts like friendly and helpful enforcement.

When did all this happen Colin?

So, what's the new minimum benchmark standard for a single Dorgard on a cross-corridor door in a small single storey office with two-directional escape?