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Smoke Detector Sensitivity Testing & Cleaning

Posted by ORR Protection on Sep 3, 2020 8:00:00 AM

During the MCFP Virtual Conference series, expert Lee Kaiser, covers testing fire alarm sensitivity. In the video below, watch as Lee dives in-depth for what goes into testing and maintenance for alarm sensitivity. 

Video Transcript:

Smoke Poles

I brought with me the newest, latest and greatest smoke pole that you could buy out there and I want to do a little demonstration with this.  I didn't bring a fire alarm system with me today but I brought a little residential smoke alarm. Since a photo electric detector is part of the smoke alarm it's going to work for this today.  It works just like a commercial system would. 

If you would look in here, that is a little photo eye.  So, inside of this one we put something in the device, the photo eye sees it and it will activate it to generate a little bit of smoke.  There's a small oil cartridge inside and a heater ran by a battery that makes the smoke.  What we're going to do is put the cup on the detector.  You'll feel the unit whirl a little bit as that fan spins up and makes a little bit of smoke and then the detector will go off.  After you'll pull it off and then put it back on because this device cleans the detector automatically after the test.  To summarize, you put it on once to test, pull it off, put it on a second time to clean it. The fan will run to blow any of the smoke or the residue of the smoke out of the detection chamber to make sure the detector lasts longer in the field over the testing period. 

Next we are going put it underneath the table curtain and pull it back out?  It's going to light up.  A lot of the spaces that we use these with are in subfloors and data centers, so it makes it easier for the technician to go out and find those detectors.

Sensitivity testing

Another test that we need to do for smoke detectors is a sensitivity test.  Sensitivity testing tests if the detector is still sensitive to smoke.  The detectors list a minimum sensitivity, so we test at the minimum acceptable sensitivity to smoke.  A couple things cause smoke detectors to get less sensitive smoke over time.  One of the things is dust.  Dust that's normally present in the air gets into the detection chamber and builds up.  That will cause the detector to be less sensitive to smoke. 

Another thing that happens is the electronics inside the detector will age and over time they will become more resistive to electronic current flow and that will impact the sensitivity and they'll get less sensitive.  Some fire alarm panels are automatically arranged to deal with that and we call that feature drift compensation.  Some addressable intelligent panels have drift compensation built into the unit so they'll automatically detect it and make a detector more sensitive to smoke to deal with degradation over time.

Sensitivity testing is not done on an annual basis.  It is done the first year after installation and then every 2 years after that. If we document good performance, there's an option to extend it to 5 years, but there needs to be records of us doing the tests and provide that to the authority having jurisdiction so they can see that we're doing that testing. 

There are a number of options to perform sensitivity testing.  One of the ways is using the calibrated test method that the manufacturer describes. One example is with an older style Fenwall detectors, there's a couple terminals that you can put a meter against and measure the resistivity of that device. Then that reading corresponds to a sensitivity on a table that the manufacturer provides that you can see if it is within specification or not. 

Another example is a Fike IR tool. For some Fike detectors that are installed, you can use their IR tool for testing.  It looks like a remote control and it sends a beam of infrared light up to the detector and the detector reports back to the IR tool the sensitivity. 

The next example is a solo sensitivity tester. It takes about 8 minutes per detector to establish the sensitivity of that device and see if it's within the specifications. This device is known as a Gemini detector.  Gemini testers are still out there, but most of use automatic sensitivity testing.  Many of today's addressable fire alarm panels automatically do the sensitivity test so when the panel sees that the detector is out of sensitivity, it will generate a sensitivity trouble signal at the panel.  That's a feature that the fire alarm panel manufacturers  have included to help reduce the cost of maintaining their systems. 

Benefits of regular testing and maintenance

When we find a detector that's out of sensitivity we've got to do maintenance on it and we do maintenance on those detectors by cleaning them.  That's really the only maintenance that we can do to a smoke detector. So when we find a detector is out of its listed sensitivity range we clean it or we replace it.  If we clean it and it returns to its normal sensitivity, great.  If it doesn't, then our only option is to replace it. 

There are also routine cleanings based on the manufacturer's recommendations.  They'll make recommendations on their systems for detector cleanings so you can avoid false alarms.  If you have a fairly dusty room, you may want to clean your detectors more often so you don't have false detections. 

The cleaning method that we prefer is vacuuming.  Our technicians use little Dewalt battery powered vacuums to go around and vacuum out detectors.  Some people use compressed air but we prefer the vacuum method.  The vacuum method is what we've established as a best practice.  Another best practice that we recommend is yearly cleaning.  We suggest that you write that into your service contracts that your detectors get cleaned every year.  We have found that for our customers that we do that for, their systems last longer.  Some buildings that our systems have been installed in have had the same detectors as first day they were installed 35 years ago by using this practice.  Without proper maintenance a normal detector will last in a building between 10 and 15 years. With proper maintenance and cleaning, we can extend the life of those detectors. 

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