A critical aspect of an emergency voice/alarm communication system (EVACS) is the ability to understand the message and respond. A temporal pattern is easily comprehended even if the message does not come through clear. In the event serious damage or an unknown danger in the building, clearly communicating the message to shelter in place vs. get out is important.
Background noise can have a significant impact on the emergency message. The location of HVAC vents, fans, and compressors can provide a constant low level noise. Additional sources of background noise can be traffic, truck deliveries, and airplanes (commercial and military). A 10dB boost to the voice signal can overcome some background noise. A frequency analysis can be performed in areas with consistent noise like factory floors.
Reverberation can occur when the message is reflected back at the listener muddling the original message almost like listening to two conversations. The construction materials and wall arrangements affect how the sound is absorbed versus being returned to the source.
Carpeted floors and softer materials absorb the stray frequencies, where concrete and steel scattered the message in multiple directions. This is a difficult factor to address and may require professional analysis and specific speaker locations.
Distortion in the original message can occur when the voice message is sent to the speaker with too much power. The speaker is overdriven and the message is not produced clearly.
It may still be under stood, but it may take longer to comprehend.
The NEMA SB 50 Emergency Communications Audio Intelligibility Applications Guide is a good source of information on the topic of intelligibility.
The only reason to give priority over the fire alarm is because the situation would result in greater risk to the occupants like domestic terrorism with individuals targeting businesses and coworkers. Pulling a fire alarm pull station to evacuate the building into a potential armed assailant or an area with an explosive device could be one method to use the evacuation system against the occupants.
Distance High dB Low dB Candela
10 feet 84.4 79.4 15
20 feet 78.4 73.4 15
30 feet 75.4 70.4 30 (28’)
40 feet 72.4 67.4 75
58
NFPA 72 24.4.3.1.7 allows the level of the recorded messages to be determined by the emergency response plan (ERP), and 24.4.3.1.8 specifically allows the ERP to higher priority than fire alarm activation. NFPA 24.4.3.2.9 requires a manual means to relinquish control of the fire alarm system at each mass notification location. A copy of the Fire Safety Management Plan in accordance with PFC, Chapter 4 is provided in the Appendix M.
Terrorism related events is a required section of emergency plans. Other situations could be a local chemical release producing hazardous conditions and simultaneously there is a fire in the facility. The potential risks must be weighed and a response planned
anticipating such events on a general scale.
ALARM AND TROUBLE SIGNALS
Water flow devices are provided at the lateral connection to each riser on each floor for each zone. Electrical supervision is provided on all sprinkler control valves with tamper switches. On site and Central Station Monitoring is provided for all alarm and trouble signals.
FIRE PUMP
The fire pump is located on the ground floor in a mechanical room. Signals are provided for supervisory, trouble, and pump running notification. The fire pump is an electric fire pump, and provides with emergency power from the emergency generator to ensure operation in the event of a power failure.
KITCHEN HOOD EXTINGUISHING SYSTEM
All Type I hoods are protected by wet chemical extinguishing systems with high
temperature heads and manual pull stations per NFPA 17. These systems are required to be connected to the fire alarm system to initiate an alarm if activated.
HEAT DETECTION
Heat Detectors are provided in the elevator shafts per NFPA 72 section 21.3 and 21.4.
Activation of the heat detectors shunt the elevator power.
CARBON MONOXIDE DETECTION
Carbon monoxide detection is provided in areas where fuel burning equipment is located per PFC 908.8.1. The system are installed per NFPA 720. In the event of a high CO
concentration a local alarm sounds and a supervisory alarm sounds at an occupied location.
59 REFRIGERANT DETECTION SYSTEMS
Machinery rooms with refrigeration equipment that could cause a hazardous condition if a refrigerant leak were to occur as required to have a refrigerant leak detector actuated at a value corresponding to the TLV-TWA values in the IMC. Most refrigerants are odorless and colorless making them hard to detect. If a large leak occurs victims are typically
incapacitated with their rescuers. The detectors are required by PFC 606.8 to have audible and visual alarms. Detectors and alarms are required to be placed in approved locations in accordance with NFPA 72 and PFC Section 907.5.2 and 907.5.2.3. Alarms are required inside and outside of the space and detection sample lines are required to be located at floor level and potential leak points.
ELEVATOR SYSTEMS
Elevators will be provided with smoke detection on each level within 21 feet of the elevator door per NFPA 21.3.5 to initiate Phase I recall. Additional smoke and heat detectors are in provided in the elevator machinery rooms as required.
A detailed description of Elevator function is discussed in the Elevator section.
ECONDARY POWER SUPPLIES
i. Secondary power supply calculations follow the requirements of NFPA 72 section 10.6.7.2.1.
ii. Battery calculations shall include 20 percent safety margin.
iii. The secondary power supply for in-building emergency voice and mass notification systems shall operate in standby for 24 hours and in alarm for 15 minutes.
iv. Speakers for the voice evacuation system are powered from the main VECP on the main floor. Strobes are powered by a separate remote power booster supply.
v. Sounder bases with a 520 Hz audible signal for the dwelling room smoke alarms are powered by a separate remote power booster supply.
vi. Strobes in the hallways and restrooms are powered by a separate remote power booster supply.
60 FIRE ALARM MATRIX
The specific operation sequence of the fire protection systems should follow the example in Figure 19 from NFPA 4 Standard for Integrated Fire Protection and Life Safety System Testing which provides a detailed example of a fire alarm sequence of operations.
FIGURE 19. SEQUENCE OF OPERATIONS FROM NFPA 3 FIGURE A.3.3.23(a)
61 PATHWAY SURVIVABILITY
Per NFPA 72 section 24.3, the method of evacuation is floor evacuation and requires a Level 0-3 pathway survivability. A risk analysis is required to be performed to determine the necessary level of survivability. A dedicated amp is provided for each floor and not shared between floors.
ACCESS CONTROL
The residential dormitory towers are accessible through the security station located in the south tower. All student residents have identification cards that are scanned when entering the elevator lobby. The North and South Towers primary access point is the four elevators.
Students in the north tower must take the elevator to the desired floor and then cross the open air bridge to the other side. The egress stairways are not accessible from the ground level and are locked to prevent entry from the stairways.