Your questions answered: Fire/life safety: Notification systems

NFPA 72 defines how fire notification systems should be designed and installed. Here is additional information from the Oct. 13, 2016, webcast on Fire/life safety: Notification systems.

By Ray Grill, PE, FSFPE, Principal, Arup, Washington, D.C. October 20, 2016

NFPA 72: National Fire Alarm and Signaling Code provides design and installation provisions for fire signaling, emergency communication, and mass notification systems. These systems are used not only to notify occupants of fire emergencies, but also cover emergencies such as weather events, terrorist events, and other threats.

Questions not addressed during the Oct. 13, 2016, webcast on Fire/life safety: Notification systems are answered here by Ray Grill, PE, FSFPE, Principal, Arup, Washington, D.C.

Question: Please describe options to test intelligibility, accuracy, and acceptability to authorities having jurisdiction.

Ray Grill: NFPA 72-2016: National Fire Alarm and Signaling Code requires voice system to be intelligible and defines intelligible as being clear and understandable. A way of testing intelligibility is to have a prerecorded message play to verify that the message is understandable in areas that can be occupied. The U.S. Dept. of Defense does require quantifiable measurement of intelligibility. Testing can be performed as described in Annex D of NFPA 72. If quantifiable testing is required, a talk box is used to play a calibrated signal into the microphone of the system. An intelligibility meter is used in the field to measure the level of intelligibility where intelligible voice is required.

Q: What is involved in designing notification systems for empty shell spaces where the final occupancy classification requires full notification after it is built out.

Grill: Designing notification for an empty shell space can be challenging. The potential uses of the space should be considered. In office buildings, a good estimate of the final needs of the space can be made to ensure the infrastructure is designed to accommodate the final built out condition. A 20% to 25% cushion on the capability of notification appliance circuits is also good practice.

Q: Are notification devices required in an office with two desks?

Grill: The definition of a work area can be a little subjective. Spaces that get assigned to a worker would typically be considered a “work area” and not be required to have visible notification appliances unless the workers assigned to the space are impaired. Common and public areas are required to have visible notification. I would not consider an office that is shared by two people to be a common area requiring visible notification.

Q: Regarding area of refuge two-way communication, is this a fire phone or a general telephone?

Grill: The area of refuge two-way communication system allows a disabled person to call for assistance on a 24/7 basis. The code does not define the type of system. The portions available to the public must be accessible. Some systems operate using an autodialer similar to the two-way call system required in elevator cars. Some systems operate use voice over Internet protocol communication.

Q: What is a fully sprinkled building? NFPA provides various exceptions to the provision of sprinklers. If sprinklers are not provided in all locations, is the building not fully sprinkled?

Grill: A fully sprinklered building is a building that has a sprinkler system compliant with either NFPA 13-16: Standard for the Installation of Sprinkler Systems, NFPA 13R (residential four stories or less), or NFPA 13D (one and two family dwellings). These standards allow certain areas of a building to not be provided with sprinklers (i.e., noncombustible concealed spaces). Taking advantage of these allowances does not preclude the building from being considered fully sprinkler protected.

Q: What is considered to be an acceptable location for a battery backup unit of an emergency responder radio coverage system?

Grill: NFPA does not identify a specific location for a battery backup unit. At a minimum, I would locate it in an area that is not accessible to the public and in a room that has appropriate environmental controls (ventilation, etc.).

Q: How did the Washington, D.C. rooms quantify on the CIS or STI scale? Please define CIS and STI again.

Grill: Quantifiable measurement was not performed on the spaces in the examples of the office in Washington, D.C. “CIS” is common intelligibility scale and “STI” is speech transmission index. Discussion of these can be found in Annex D to NFPA 72.

Q: What is the source for the U.S. Access Board example diagram shown?

Grill: Follow the embedded link: U.S. Access Board

Q: Are multilingual notification systems available, and do codes allow such notifications?

Grill: Messages can be recorded in multiple languages. The language used should be consistent with the most common languages used by the occupants of the building in which the system is installed.

Q: Do low frequency sounders need to be synchronized with the sounders in a hallway area?

Grill: NFPA 72 requires the standard evacuation signal to be synchronized within a notification zone. The intent is to preserve the temporal pattern to an occupant within the space. If you are talking about a hotel room or apartment versus a public corridor, I would say that there isn’t a need to synchronize the signals.

Q: Please provide clarification of the “common use” definition.

Grill: Defining common use can be subjective. I would suggest reviewing the U.S. Access Board guidelines.

Q: What possible solution can be applied in an acoustically distinguishable space (ADS)?

Grill: Assuming you mean an ADS that has challenging acoustical characteristics, various approaches can be pursued. One may be the use of linear array speakers to enhance the intelligibility of messages. Adding acoustical materials to reduce reverberation is usually not an option.

Q: Is there software available to test the audibility or intelligibility during the design process, similar to a photometric plan?

Grill: Yes, there is software available. One product is called “Ease.”

Q: Under the occupancy driven system drivers, what about stadiums, arenas, etc.?

Grill: These occupancies fall into the assembly category with more than 1,000 people and would require voice evacuation. There are some exceptions and allowances for facilities such as these that have trained staff on duty to manage occupants and evacuation. Live messaging is usually preferred.

Q: Can you briefly talk about the use of a paging system for voice messaging in conjunction with the fire alarm system?

Grill: It is challenging to talk about this subject briefly, but NFPA 72 does allow the use of a paging system in conjunction with a fire alarm system. Paging systems can receive line level audio signals and control signals from a fire alarm system to rebroadcast messages. See Chapter 24 of NFPA 72.

Q: Are fire alarm notification devices required in private offices with conference tables?

Grill: A private office is not required to have visible notification. Fire alarm system audibility is required in occupiable areas. An audible device outside the room could deliver the required audibility if it were designed to do so. For the marble wall lobby, lower power output speakers located on the wall about every 10 feet should do the trick.