Strobes Flash When Fire Alarm Silenced

End Users, AHJs (Authority Having Jurisdiction) and Technicians seem to think that fire alarm strobes are required to continue flashing when the fire alarm control unit or panel is silenced.  

FACT #1:  There is not and never has been anything in the code that requires the fire alarm visual notification appliances AKA Strobes to continue flashing once the fire alarm control panel has been silenced.   

FACT #2:  NFPA 72 2013 Section 10.13.2: “When an occupant notification alarm signal deactivation means is actuated, both audible and visible notification appliances shall be simultaneously deactivated."

So Why did we have Strobes Flashing when the Fire Alarm System has been Silenced?

From what information I have been able to gather, this function crept into the minds of installers and inspectors sometime in the 1980's. The thought of having strobes continue flashing while firefighters validated the alarm condition was a plus.  Firefighters could communicate via their radios without the loud distraction caused by the audible signal.   Lastly, individuals looking to enter a facility would see the visual appliances flashing and know not to enter due to a potential threat of a fire.

This is an argument that comes up less as time moves forward, however, some people are stuck on the ability to have strobes continue flashing during a fire alarm system silence.  Please note that while NOT required by any code or standard, this can still be required within a particular building specification or City Ordinance.

The function can be done by most manufacturers and is not hard to accomplish.  However, it does not make sense to have it enabled and that is why you will not find it in any code references.  Strobes where brought into the code for ADA adaptability.  With that said, does it make sense to leave the strobes flashing if you silence the fire alarm?

Ask yourself, "How is a deaf person affected by this feature?".

When a fire alarm system is activated, a hearing impaired individual will see the strobes flashing but NOT hear the audible tone.  Once the fire alarm panel has been silenced and the audible tone is cut off, this individual has no idea the fire department is on scene, the system as been silenced and the event is being investigated.  To this individual there is still an active evacuation scenario in place until the fire alarm panel has been reset.

Ask yourself, "How is a blind person affected by this feature?".

When a fire alarm system is activated, a visually impaired individual will NOT see the strobes flashing but will hear the audible tone.   If the fire alarm system is silenced and the audible tone is cut off, this individual will have no idea there is still a potential treat in the building.  They could potentially return to their business when in fact there is an active fire alarm investigation occurring in their close proximity.  Another point noted above was the ability for flashing strobes to notify individuals to not enter a building as it is being investigated for a fire.  If you are blind, you would not be aware the fire alarm system is activated and under investigation.  The blind individual could potentially walk right into harmful or fatal situation.  

In my mind this is why NFPA 72 2013 directly addresses this situation in section 10.13.2.  If we agree to just cut off both audible and visual signals in the event of a system silence, we are not favoring or discriminating against anyone with or without a disability.

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Have you freshened up on the newer fire alarm LED strobe technology?

Wheelock LED Notification Appliances

Are the new Wheelock LED Series Notification Appliances all They're Cracked up to be?

Although the Wheelock LED (Light Emitting Diode) notification appliances are not so new anymore, they still seem to bring up quite the conversations.  Like any new fire alarm equipment, it is wise to let them prove themselves before you actively start specifying and installing them throughout all of your sites.  Well that time has come and gone as these LED strobes and horn/strobes have been flying off the shelves.

Our goal here is to make you aware of their capabilities so that you can decide when and when not to include them in your fire alarm system design criteria.  For this comparison I am going to be using the new Wheelock LED Series Horn/Strobe (model LHS) and the Older Wheelock Exceder Series Horn/Strobe (model HS).  Note that both models comparisons will be based off wall mounting, 24 VDC, 3 Tone Temporal Output, and set at the High Setting.  This should keep everything fair for the sake of the article.

Lets take a look at differences and similarities of the two notification appliances.

As you will notice from the chart I created above, the two notification appliances have quite a few differences.  One of the more noticeable differences is the candela selection available.  You can see that the Exceder series covers standard candela all the way up to high candela at 185 CD.  On the other hand the Wheelock LED series appliance only covers the standard candela range.  

Now the biggest item that everyone is discussing around the new LED series strobes is the lower current draw.  We all know the lower the current draw, the more appliances we can fit on a circuit. More appliances on circuits results in few circuits, and less remote power supplies.  As you may notice in the "Current Draw" tables above, the LED series appliances have a lower current draw through the range of 15 CD - 75 CD.  Once you jump up to 110 candela, the standard Exceder series with Xenon bulb actually draws less.

It all depends on you application as your facility may demand more 110 candela strobes in comparison to your lower levels (15-75).  In this case you would probably want to stay with the older Exceder Xenon bulb technology.  Now if you have an office building with multiple corridors, you can get away with 15 candela and the LED strobes would be your best bet.

*It is also very important that I make you aware that Cooper-Wheelock has made it clear that both the Xenon bulb and LED style visual appliances are compatible on the same circuits and will successfully SYNC if you use the proper remote power supply or sync module such as the DSM-12/24.

I hope this information assists you in your design as both models are great products with their own special characteristics.