Glass-Break Do’s and Don’ts

Tech expert Bob Dolph shares best practices for professional acoustical glass-break detector application, installation and maintenance.

Glass-Break Do’s and Don’ts

Do you do windows? No, I don’t mean cleaning them, though your customer might appreciate the gesture. As you may have already guessed, I am talking about protecting windows and similar openings. What are some of the industry’s best security practices? This is our discussion for this month’s Tech Talk.

Acoustical glass-break detectors (AGBD) over the years have matured greatly. So much so that you see them everywhere in every professional and DIY alarm system today. Did you know that the Amazon’s Alexa even now has an AGBD app? Good, bad, you decide.

With this popularity of today’s AGBDs should give one confidence in their successful performance, right?

As Johnny Carson would say, “Not so fast, O Great One.” Why should we not be surprised that there is more to this technology than just sticking a device up on the wall? Let’s look at the some of the alarm science that goes into best practices for a professionally installed AGBD.

What causes an alarm activation from an AGBD? Silly question, it is the sound of breaking glass. Yes, but what kind of sound it that? Let’s take a closer look.

There are basically two types of AGBD technology. First, there’s the devices that listen for the expected unique sound signature of breaking glass. The other type of AGBD listens for a combination of a low frequency sound, often referred to as infrasonic, from the glass flexing and breaking, and a higher frequency signature of the breaking glass.

This is one of my favorite types and can be found with the Honeywell Flexguard line. Many do not know that the company also makes the unique directional FG1025EZ, which will ignore all sounds except those that come directly from the protected glass area.

Let’s take a close look at some do’s and don’ts for professional AGBD application, installation and maintenance.

DO: Read the F******* Manual (RTFM). Reliable AGBD manufacturers have taken considerable time and effort to help with your installation. In the famous words of UL 681 Standard for Installation and Classification of Burglar and Holdup Alarm Systems, Section 8.4.5,  “A shock sensor or glass break detector employed to protect a window shall be appropriate for the type of window involved and shall be installed in accordance with the product’s installation instructions.” Don’t be proven later in a court of law that you ignored the manufacturer’s directions. Keep sensor documentation for your records.

DON’T: Assume all glass is the same. You have different glass flavors such as plate, laminated, tempered and reinforced. Make sure the AGBD and associated tester (you do have one, right?) have settings for different types of glass. According to most building codes, glass around doorways and big sliding doors are a few applications where tempered and laminated glass may be used. Some other types such as large commercial display windows might be laminated. Test accordingly.

DON’T: Consider AGBD test finished with placing and activating tester near a window. If you test AGBD on new construction go back to test when the room is fully furnished, including drapes. The furnishings can absorb a large amount of sound intensity. You may find final AGBD placement behind window drapes. Always plan on the side of caution. Place AGBD as close to windows but avoid false alarms. Additionally, something you will only hear about here is the danger of no alarm from high sound level saturation. Many AGBDs when placed close to a very large glass section, such as a commercial display window, may be overwhelmed and just cancel the actual glass activation. Check with the manufacturer of sound saturation specifications, you may be surprised.

DO: Use only testers and simulators recommended by AGBD manufacturer. Clapping hands or throwing your keys against the wall will test that the AGBD is working, but will it properly detect a broken window? There is more to it and as a pro you know that. I just recently read a DIYer’s comment, “I installed the device and just pray it will work.”

DO: Provide an annual maintenance program for professionally testing AGBDs. This is another good opportunity for additional RMR as room environments change and can affect the AGBD performance.

DON’T: Forget to take some time to educate and train customers on their sensor technologies. This will help to reduce false alarms.

Some other window-related alarm technologies to consider include shock sensors that can be applied to the glass or window frames. Most have sensitivity adjustments. Some well-known are the USP Window Bug, Honeywell ASC-SS, Texecom Premier and Tane MA-100T.

There’s also exterior PIR barriers such as the Optex BX-80NR, alarm window screens such as Security Screens Inc.’s adjustable alarm bars and the GRI Window Bar. Physical glass security enhancements such as applying 3M Security Window Film and Riot Glass is another option, though these will affect AGBD performance.

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About the Author


Bob is currently a Security Sales & Integration "Tech Talk" columnist and a contributing technical writer. Bob installed his first DIY home intercom system at the age of 13, and formally started his technology career as a Navy communication electronics technician during the Vietnam War. He then attended the Milwaukee School of Engineering and went on to complete a Security Management program at Milwaukee Area Technical College. Since 1976, Bob has served in a variety of technical, training and project management positions with organizations such ADT, Rollins, National Guardian, Lockheed Martin, American Alarm Supply, Sonitrol and Ingersoll Rand. Early in his career, Bob started and operated his own alarm dealership. He has also served as treasurer of the Wisconsin Burglar and Fire Alarm Association and on Security Industry Association (SIA) standards committees. Bob also provides media and training consulting to the security industry.

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