# duct smokes



## cheyer (May 9, 2010)

Curious to see how other AHJ's are having f/a contractors perform acceptance testing of duct smokes (i.e canned smoke, magnet, etc.)

Thanks.


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## FM William Burns (May 9, 2010)

What the manufacturer allows, some will not allow the use of canned smoke. We also allow them on the supervisory circuit in some applications.


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## cheyer (May 9, 2010)

Thanks, FM.

In our jurisdiction, all new installations are usually always on the supervisory circuit as well.


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## cda (May 9, 2010)

I mainly check to make sure tubes are installed right, shut down happens, and then sometimes just smoke the head.

do not fire bomb them


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## fireguy (May 10, 2010)

We have tried canned smoke and found it only works if the air movement is off.  Otherwise the air blows the smoke past the sampling tube, w/o any smoke going into the sampling tube.

We use a magnet, which meets some mfg requirements, but does not test the air entering the sampling tube.

A problem we normally find is the sampling tube is plugged with dust and dirt.

I am not satisfied we are testing duct detectors to the intent of the code by using magnets and turning off the air movement.

Two  testers I have been thinking about  http://www.sdifire.com/cms/document/ductchecker_flyer_LI32191_1.pdf

http://www.sdifire.com/cms/document/avchecker_flyer_LI32188_1.pdf

Does anyone have any experience with either of these tools?


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## FyrBldgGuy (May 10, 2010)

When it comes to Duct Detectors I always try to get the same message across... Just don't do it if there is another way.  I have been working with clients to use area detection.  Over 30 years of working with duct detectors I have never found them to be reliable.

As a fire fighter I have responded to many false alarms with duct detectors and have also found the opposite, duct detector did not operate with smoke present.

You can use any method to test and you still will not have assurance of reliability with duct detectors.


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## cheyer (May 10, 2010)

FG and FBG, good info...our Dept. is just now starting to test these devices during initial acceptance. The building inspectors were the only ones doing it prior as part of their mechanical....I felt we should be double checking these as well.


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## Dr. J (May 10, 2010)

Why would any of you use any test other than what is required by NFPA 72 and the manufacturers?  The requirement is quoted in the product data sheet posted by fireguy, and is also listed in the manufacturer's installation instructions http://www.systemsensor.com/pdf/I56-3050.pdf .  The required test is to check that the sampling tubes have the differential pressure avialable to draw duct air into the detector housing, and/or that the proper duct velocity is present.  Canned smoke will not do this, and magnets definately will not.  You might as well just use a remote key switch.  All canned smoke/magnets/remote key switch can do is to check to see that the proper sequence (AHU shut down, damper closure, etc) occurs once the duct detector is in alarm.

FBG - I agree with you that duct detectors are unreliable.  That is why they are not acceptable as a substitution for area detectors.  However, the issue is that in most cases, the only way to get away from duct detectors is to have total coverage area smoke detection.  Regarding the false alarms, several of the AHJs around here require that duct smoke detectors are supervisory signal only, just to avoid rolling the trucks every time a piece of lint gets sucked into them.


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## fireguy (May 12, 2010)

Another problem with testing duct detectors is finding them.  Our proposal  reads " Duct detector locations need to be marked prior to the service, as per NFPA 72-2007, Section 5.16.5.4. "    We have spent more time trying  to find the detector than peforming  the test.

Dr J, my alarm tech and I will be discussing changing our test procedure because of the System Sensor information.  I have a meeting with 3 of my local FM about sprinkler testing, and we will also discuss duct detector testing.


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