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Saturday, December 31, 2016

Voice Intelligibility for Accurate Occupant Notification

Voice Intelligibility for Clear Evacuation Message
Do you know the reason behind modern fire alarm systems?  They are intended to recognize a potential life threatening fire situation such as smoke, flame or heat.  It is then their responsibility to alert the masses.  If the whole point to a fire alarm system is to alert and inform occupants, then what good does it do if these occupants can not understand the evacuation message?  This is what prompted the National Fire Protection Association or NFPA to change the title of NFPA 72 from the National Fire Alarm Code to the National Fire alarm and Signaling Code first seen in the 2010 edition.

Side note:  Did you know that NFPA 72 is not a Code reference rather a Standard?  Learn more in this article title Fire Alarm Codes vs. Standards.

I am sure seasoned fire alarm system designers have had this pounded into their heads by now but news flash, fire alarm notification signals are no longer the priority in some scenarios.  We have always been taught that our occupant notification alert or evacuation messages were to take precedence over any other audio or tone.  To an extent this is still correct including outputs such as Musak, Public Address or P.A.,  Concert or Performance Audio, etc.  There are now and have been for some time, fire alarm systems incorporating additional features that make up what is known as Mass Notification.  The alert tones, voice messages and canned message instructions of a mass notification system are to take priority over any fire alarm notification output.  This was the reason behind the revision and extended title of NFPA 72.  The National Fire Protection Association added the word "Signaling" to the title of NFPA 72 as well as chapter 24 covering Emergency Communication Systems (ECS).  NFPA 72 does not cover every aspect of Mass Notification system design.  If you are seeking additional information on the requirements of these systems, you will need to obtain a copy of the Unified Facilities Criteria (UFC) document titled "Design and O&M: Mass Notification Systems"

If you research the document above, you will become aware that Mass Notification adds a lot of new criteria to the design and engineering of a given fire alarm system, however this article will serve to inform readers on the importance of a term known as Voice Intelligibility.  If you consult the Annex D of your 2013 NFPA 72 (starts on page 311) you will find all the information pertaining to voice intelligibility.  Below we are going to touch on some of the important factors to keep in mind when up against a mass notification system that must meet specified voice intelligibility measurements.

    voice intelligibility can you hear me now
  1. What exactly is voice intelligibility?  Voice intelligibility is a measure of how comprehensible speech is in given conditions.  Voice Intelligibility is affected by the quality of speech signal, the type and level of background noise, reverberation, and for speech over communication devices, the properties of the communication system.  The concept of voice intelligibility is relevant to several fields, including phonetics, human factors, acoustical engineering and audiometry.
  2. In order to meet the criteria of NFPA 72 as well as the UFC, you will need to have what is known as a risk analysis drafted up by a fire protection engineer.  A risk analysis is an individual plan for a specific facility.  This plan includes a multitude of criteria based on potential risks and threats at the given facility.  This risk analysis will breakdown segregated areas of the building and how to evacuate or hold occupants based on individual threatening scenarios.  The risk analysis will also explain acoustically distinguishable spaces or ADS.  As defined by NFPA 72 2013 D. - An acoustically distinguishable space can be an emergency communication system notification zone, or subdivision thereof, that can be enclosed or otherwise physically defined space, or that can be distinguishable from other spaces because of different acoustical, environmental, or use characteristics such as reverberation time and ambient sound pressure level.  The ADS might have acoustical design features that are conductive for voice intelligibility, or it might be a space where voice intelligibility could be difficult or impossible to achieve.
  3. Once evacuation or staging areas of the facility are understood, we will need to design the audio potion of the mass notification system.  This is where voice intelligibility comes into play.  Keep in mind the differences between audibility levels (dB) and Voice Intelligibility.  For lack of better terms, one defines the sound pressure and the other defines the clarity and comprehension of the audio.  Just because you meet the intent of NFPA 72 chapter 18 in regards to dB levels does not mean you have accomplished an acceptable measurement of voice intelligibility.
  4. How do you measure voice intelligibility?  Unlike the use of a dB meter for audibility, voice intelligibility is a little more tricky.  There are two scales used to measure intelligibility.  One is the CIS scale which stands for Common Intelligibility Scale and the other is STI or Speech Transmission Index.  To acquire this reading you will need..... You guessed it, a Voice Intelligibility meter.   
  5. What is a passing measurement for voice intelligibility?  The voice intelligibility of an emergency communication system is considered acceptable if at least 90 percent of the measurement locations within each ADS have a measured STI of not less than 0.45 (0.65 CIS) and an average STI of not less than 0.50 (0.70 CIS).  The measurement shall be taken from an elevation of 5 feet or any other elevation deemed appropriate based on occupancy.  In areas of the facility where sound levels exceed 90 dB, it may be impossible to meet these voice intelligibility measurements.  In these cases other methods such as LED signage, etc. may be used.  For reference the STI scale can be converted to CIS via the following calculation:  CIS = 1 + log (STI).
voice intelligibility meter CIS scale and STI scale

There are a ton of factors to take in when designing a mass notification system to meet the voice intelligibility requirements of NFPA 72 and the Unified Facilities Criteria.  This article is meant to touch on the main points and get you going in the right direction.

If you are in the market for a dependable voice intelligibility meter, I highly recommend the VOX01 from SDi.  This unit is compact, sturdy, very easy to use and comes packed with tons of features and abilities.  Here is a direct link to SDi's webpage containing information on the VOX01.  Below is a video of me revealing the VOX01 when it first came to market.  Feel free to check it out and let us know if you have any questions.  

Fire Alarm Codes vs. Standards

What is the difference between fire alarm codes and fire alarm standards?

The terms "code" and "standards" are commonly used to represent the same thing.  However, the two terms stand for completely different meanings.  Fire alarm codes are written rules and regulations that are then adopted as law for enforcement by an AHJ or Authority Having Jurisdiction.  Fire alarm codes once put in place, are the minimum requirements that must be complied with to provide a reasonable degree of life safety. Codes are written based on standards.  Fire alarm standards are generally produced by a consensus or technically committee to represent a minimum level of how to install certain types of protection.  Standards are focused on one particular system component and give guidelines on the proper installation, maintenance and inspecting.

NFPA 101 Life Safety Code Book
Fire Alarm Code:

Fire alarm codes specify when and where a given type of protection is required.  These fire alarm codes are a minimum requirement and are encouraged to be exceeded.  Below is a list of fire alarm and fire related code references:
  • NFPA 30 (Flammable and Combustible Liquids Code)
  • NFPA 54 (National Fuel Gas Code)
  • NFPA 70 (National Electrical Code)
  • NFPA 101 (Life Safety Code)
  • NFPA 5000 (Building Construction and Safety Code)
  • IBC (International Building Code)
  • IFC (International Fire Code)
Fire Alarm Standard:

Fire alarm standards detail how a specific protection required by the code is to be achieved.  Below is an example list of fire alarm and fire related standards:
  • NFPA 10 (Standard for Portable Fire Extinguishers)
  • NFPA 13 (Standard for the Installation of Sprinkler Systems)
  • NFPA 14 (Standard for the Installation of Standpipes and Hose Systems)
  • NFPA 20 (Standard for the Installation of Stationary Pumps for Fire Protection)
  • NFPA 72 (National Fire Alarm and Signaling Code)*
*  Keep in mind that NFPA 72 tells us how to install fire alarm systems.  It doesn't explain what type of equipment (pull stations, smoke detectors, duct detectors, waterflows, tampers) should be used.  This information can be found in the specific jurisdiction's adopted building code.

How you determine the Fire Alarm requirements.

Check with your local authority having jurisdiction to determine what edition of the applicable codes they are currently enforcing.  Most codes will determine the fire alarm and automatic fire sprinklers based on the occupancy classifications of the particular building.  If NFPA 101 Life Safety Code is enforced, consult section 9.6 for the exact system installation requirements.

Tuesday, December 20, 2016

Low Frequency Sounders for Fire Alarm Evacuation

Are Low Frequency Sounders Being Enforced by your AHJ

Is your jurisdiction enforcing the new code mandated 520 Hz low frequency sounders for fire alarm audibility yet?  If so how are you tackling this new requirement?  And finally did you know that the smoke alarms within the sleeping rooms and guest units do not need to meet the 520 Hz requirement?

When did this start?

System Sensor Low Frequency Sounder and Sounder StrobeNot a lot of people are aware that this requirement was originally noted in the (2010) NFPA 72 National Fire Alarm Code section  It states "Effective January 1, 2014, where audible appliances are provided to produce signals for sleeping areas, they shall produce a low frequency alarm signal that complies with the following:
(1) The alarm signal shall be square wave or provide equivalent awakening ability.
(2) The wave shall have a fundamental frequency of 520 Hz +/- 10 percent.

Now we fast forward to 2013.

Note that the (2013) NFPA 72 Fire Alarm and Signaling Code requirements are the same found in Section

Now lets break it down.  There are a lot of code sections so stay with me.

The Annex A of NFPA 72 (2013) section A18.4.5.3 lets us know that this section does not cover the audible requirements of single and multiple station smoke alarms and instructs us to consult chapter 29 for said requirements.

If you refer to Chapter 29 "Single and Multiple-Station Alarms and Household Fire Alarm Systems" section 29.3.6 it states the following: "All audible fire alarm signals installed shall meet the performance requirements of 18.4.3,, and 29.3.8."  Please notice that this section does not include section This may lead one to believe that single and multiple station smoke alarms for dwelling units do not need to meet the new 520 Hz low frequency requirements.

The key section to pay attention to here is section 29.3.8 which states "Notification appliances provided in sleeping rooms and guest rooms for those with hearing loss shall comply with and, as applicable."

Section "Mild to Severe Hearing Loss.  Notification appliances provided for those with mild to severe hearing loss shall comply with the following:

(1) An audible notification appliance producing a low frequency alarm signal shall be installed in the following situations:

    (a) Where required by governing laws, codes, or standards for people with hearing loss.
    (b) Where provided voluntarily for those with hearing loss.

(2) The low frequency alarm signal output shall comply with the following:

    (a) The waveform shall have a fundamental frequency of 520 Hz +/- 10 percent.
    (b) The minimum sound level at the pillow shall be 75 dba, or 15 dba above the average ambient sound level or 5 dba above the maximum sound level having a duration of at least 60 seconds, whichever is greater."

Section "Moderately Severe to profound Hearing Loss.  Visible notification appliances in accordance with the requirements of and tactile notification appliances in accordance with the requirements of section 18.10 shall be required for those with moderately severe to profound hearing loss in the following situations:

(1) Where required by governing laws, codes, or standards for people with hearing loss.
(2) Where provided voluntarily for those with hearing loss.

What does this mean?  

Low frequency sounder internal view speaker coneIf we read section 29.3.8 very carefully you will notice the word "AND" between sleeping rooms and guest rooms for those with hearing loss.  This is telling us that the requirements of section and apply to ALL sleeping rooms including guest rooms for those hard of hearing.

How does this effect your design?

To this date there are no UL listed UBC smoke alarms that can produce an audible tone at 520 Hz.  In fact the only manufacture that has a UL listed 520 Hz low frequency sounder appliance is System Sensor.  This means no more mini horns in the sleeping rooms of R-1, R-2 and R-2.1 occupancies.  The only way to accomplish this is by installing a System Sensor HW-LF (low frequency sounder) or addressable smoke detector with low frequency sounder base in place of all mini horns.  This will give us the required 520 Hz in all sleeping areas during a general alarm condition.

How do we accomplish 520 Hz when the Single or multiple station smoke alarm is activated?

Since there is no such thing as a low frequency LISTED smoke alarm, I propose installing addressable system smoke detectors in all sleeping rooms and guest rooms.  On top of this an addressable control module will need to be installed for each residential unit.  The control module will then need to be wired so that it controls an individual NAC (Notification Appliance Circuit) for that particular unit.  Through programming we can activate this individual control module upon activation of any smoke detectors within the unit.  Lastly the control module for each unit will need to be mapped to activate during a general alarm condition.  This way we are activating the in room low frequency sounders via the in room smoke detectors as well as any building wide general alarm device.  This method allows us to accomplish the requirements of section as well as 29.3.8 with listed equipment and methods.

How does this effect your final cost?

Obviously there is a lot more equipment needed to perform this requirement such as addressable system smokes and control modules.  On top of this the low frequency sounders are more expensive than mini horns.  Also note that the new low frequency sounders draw more current than mini horns which will decrease your total allowable appliances per NAC ultimately increasing the number of required remote power supplies.

This is going to be a huge adjustment for our industry which will ultimately comes with a large learning curve.  I suggest your contact your local AHJ (Authority Having Jurisdiction) and find out what their interpretations on this subject are.

Reading Reverse Polarity with a Meter

Do you know how to Use a Multi Meter to Locate a Fire Alarm Device or Appliance that has been connected with reverse polarity?

If not this article will explain how to set the multi meter up as well as how to properly break down fire alarm circuits to locate an initiating device and or notification appliance that has been connected with reverse polarity.

Real quick we will start with the basics.  "What is polarity?"  Polarity in electrical circuits is known as "Positive" and "Negative".  In DC (Direct Current) circuits one pole is always positive (typically marked with a + or red) and the other is always negative (typically marked with - or black).  Note that electrons within a DC circuit only flow in one direction.

This is where a lot of people become confused.  There are two common notations of flow for DC circuits. See below:

#1 is the Conventional Flow Notation.  This notation is based on Benjamin Franklin's conjecture regarding the flow direction of charge.  This notation shows charge flow moving from the Positive Pole of a DC circuit to the Negative Pole.  This is the notation that is most commonly used my engineers and is technically incorrect.

#2 is the Electron Flow Notation.  This is the true notation of charge flow as it shows the actual motion of the electrons in a DC circuit.  Note that this notation shows the charge flow moving from the Negative Pole to the Positive Pole. 

Now that we have covered how a charge or current flows through a circuit, it is important to understand how a diode works and how it can allow or block this flow from occurring.

Definition of a DIODE: A semiconductor device with two terminals, typically allowing the flow of current in one direction only.  This direction of current flow moves from the ANODE side through the CATHODE side of the DIODE.  An easy way to remember this is a DIODE allows current to flow in the direction of the arrow within the symbol.

Here is the electrical symbol for a DIODE:

DIODE showing the Anode and Cathode Orientation

Below are two diagrams that depict the same image however they show the current flowing in opposite directions (conventional vs. electron flow notation).  Notice that even though they both have a diode facing in the same direction the lamp is still illuminated.  "Why is this?"  I thought that a diode only allows current to flow in one direction and that a DC circuit only flows in one direction.  "This would make it impossible to illuminate the lamp in both scenarios, right?"

Conventional Flow Notation with Diode and Lamp
Conventional Flow Notation with DIODE
Electron Flow Notation with Diode and Lamp
Electron Flow Notation with DIODE
This is correct.  However the symbol for a DIODE has never been updated to match the Electron Flow Notation.  Therefor the DIODE is always shown with the "Line" or Cathode side pointing towards the positive flow based on the Conventional Flow Notation.  Note that if we were to update the DIODE symbol and show the arrow facing the opposite direction, the diagram based on the Electron Flow Notation would make more sense.

Now on to the point of this article.  "How do I use this information regarding current flow and diodes to locate a fire alarm device or notification appliance that has been connected with reverse polarity?"

A fire alarm initiating device or notification appliance that is polarity sensitive meaning it must be connected with the correct input (positive/negative) will have an internal DIODE to restrict the current flow in one direction as stated above.  We can use the diode setting on our Multi Meter to locate any section of a fire alarm circuit that has been connected backwards or with Reverse Polarity.

How it works:  When you select the DIODE setting your Multi Meter will force a small amount of current through the DIODE and measures the voltage drop across your Multi meter test leads.

Forward Bias Diodes:  If you have the Positive test lead connected to the Anode side and the Negative test lead connected to the Cathode side of the DIODE, your Multi Meter should display something close to 0.548 Volts.

Reverse Bias Diodes:  If you have the Positive test lead connected to the Cathode side and the Negative test lead connected to the Anode side of the DIODE, your Multi Meter should display OL (Open Line).

Multi Meter DIODE Test for Reverse PolarityI suggest testing a single device/appliance on a specific circuit prior to searching for reverse polarity on a fire alarm run. This can be accomplished by using a spare or by taking down a device on a circuit you need to test.  Once you have the fire alarm device or notification appliance removed, place your positive (red) multi meter test lead on the positive terminal of the equipment and the negative (black) multi meter test lead on the negative terminal of the equipment.  If your multi meter displays 0.548 Volts then you have a circuit with Forward Bias Diodes.  If your multi meter displays OL then your circuits has Reverse Bias Diodes.

Here is the key to the puzzle.  If you test the wire in your circuit and your meter displays a dead short (0.000 and typically sounds a steady beep) then your circuit has one or more devices wired backwards.  This is known since diodes in Forward and Reverse bias positions would allow the current in your circuit to travel in both directions ultimately resulting in a dead short.

Now that you know which orientation your circuit's diodes face, you can start breaking down the circuit in halves.  Each time you cut the circuit in half, read the wires in both directions paying attention to multi meter's display looking for either 0.548 V, OL or a dead short.

This easy to use Multi Meter trick will help you eliminate very time consuming labor when troubleshooting fire alarm circuits.

How to Use a Multi-Meter for Fire Alarm

Multi Meter Basics

One of the most important tools a fire alarm technician posses is the digital voltmeter or digital multi meter.  This article will explain the different settings and how they can help you track down important circuit information such as end of line resistance values, current draw, reverse polarity, dead shorts, ground faults, AC inductance and capacitance.

I cannot stress enough the importance of purchasing a quality voltmeter or multi meter.  For the purpose of the this article I will be utilizing a Fluke 117.  This is a high end meter that won't break the bank.  It has all of the key settings including a back-light for dark spaces as well as non-contact voltage detection.  In case you did not catch that last one, it will detect high and low AC voltage just by simply holding the meter close to the source.

FLUKE 117 Multi-Meter for Fire Alarm Troubleshooting

You can read more about this powerful true-rms multi meter here.

In this article we will show you how to properly tune the voltmeter or multi meter to the correct settings as well as when to move the test leads depending on what circuit information you are trying to obtain.

Now it is important to explain the different symbols and buttons so that you better understand how to navigate through this information.

Please note that although I am referencing the Fluke 117, these symbols should be close to the same on any multi meter you are using in the field.

Multi Meter Buttons and Functions:

"HOLD" This button will hold the display at the current view for documentation at a later time.  As you may know, the multi meter display may fluctuate from time to time so this button can prove to be useful if you want to lock it in at a particular time.

"MIN/MAX" As stated above the multi meter display will fluctuate between higher to lower readings.  This button can be pressed to either lock in the lowest/minimum or the highest/Maximum reading. Also note that on this meter, there is another selection with this button that will display the average between the minimum and maximum.

"RANGE" This multi meter has both manual and auto-ranging modes.  In auto-range mode the meter will automatically select the range with the best resolution.  In manual mode you must use this button to cycle through the different ranges whether it be for resistance, voltage, current capacitance, etc.

"YELLOW BUTTON" the yellow button on this meter is like a shift key.  It will allow you to select the yellow options located on the rotary wheel.

Below is a list of the most important multi meter modes and what they can be used to test for.  Feel free to click on the separate links to read further on these topics:  Please note the picture below is of a FLUKE 115 which is basically the same as the 117 minus the AUTO-V LoZ and Volt Alert settings.
FLUKE 115 Multi-Meter Settings and Uses

Selections via Multi meter Rotary Wheel:

"AUTO-V LoZ" Automatically selects ac or dc volts based on the sensed input with a low impedance input.
AC voltage from 0.06 to 600 V.
DC voltage from .001 to 600 V.

AC voltage from 6.0 to 600 mV
DC voltage from 0.1 to 600 mV

Learn More About Reading for Voltage on Fire Alarm Circuits Here.

Ohms from 0.1 ohms to 40 milliohms
Continuity beeper turns on at less than 20 ohms and turns off at greater than 250 ohms.

Learn More About Reading for End of Line Resistance, Ground Faults, Shorts and Continuity on Fire Alarm Circuits Here.

Diode test.  Displays OL (Open Line) above 2.0 V.

Learn More About Reading for Reverse Polarity on Fire Alarm Circuits Here.

Farads from 1 nF to 9999 micro Farads

Learn More About Reading for Capacitance on Fire Alarm Circuits Here.

AC current from 0.1 A to 10 A.
DC current 0.1 A to 10 A.

Learn More About Reading Current on Fire Alarm and Control Circuits Here.

"Volt Alert" Non-contact sensing of ac voltage.