Methods for constructing warning systems and evacuation management.
The warning system is the most important component of a modern security system. It is no secret that the main cause of death in fires and other emergencies is panic and uncoordinated actions of personnel.
The warning and evacuation control system (WECS) is a set of organizational measures and technical means designed to promptly inform people about the occurrence of a fire and (or) the need for and routes of evacuation (NPB 104-03).
WECS Classification
Fire safety regulations define 5 types of warning systems depending on the scale and importance of the protected facility.
Summary of types
Sound and light alarms, one warning zone.
Two or more notification zones (only the difference from the junior type is indicated).
Voice notification.
Communication of the notification zone with the control room.
Full automation of the notification system control and the ability to implement multiple options for organizing evacuation from each notification zone.
Thus, systems of all types are divided into two main groups by the presence of voice notification: types 1, 2 — signal, 3, 4, 5 — speech.
According to the Fire Safety Regulations, almost any building with a large number of people with an area of 1000 m2 or more and a number of floors over 3 floors must have a minimum type 3 fire alarm system installed, i.e., an alarm system that can warn people in the building about an emergency situation not with a siren, but with a voice message transmitted in automatic or semi-automatic mode.
If we classify the equipment for the fire alarm system, we can distinguish the following groups:
simple voice alarm systems;
warning systems combined with a broadcast system (background music, voice announcements);
digital warning systems, in which the signal from the central station to the warning point is transmitted in digital format;
wireless systems, where a radio channel is used as a data transmission medium.
The structure of any SOUE is reduced to two main elements: central equipment and a warning distribution network.
According to the method of mounting the central station, there are desktop systems and systems for mounting in a 19” cabinet. For small objects, a desktop system is suitable, it is simpler and cheaper, and there are fewer different units included in the kit. Moreover, the functionality of such a system will be at a decent level. For example, you can connect a regular office PBX to it and use the notification system for office paging. From any telephone set, by dialing a certain number, you can give a voice announcement through the notification system.
More serious systems are assembled from a large number of different units in a 19″ rack, which resembles HiFi music centers. The range of products includes power amplifiers, combined music amplifiers, CD players, cassette decks, digital tuners, control units, automation and alarms with the ability to connect to security or fire alarm systems.
Signalers
Notifiers are the face of the system, so special requirements are imposed on them. First of all, the notifier must fit organically into the interior of the room, be either invisible or complement the interior design. Here are the main types of notifiers used in the SOUE:
light — flashing light indicators, light notifiers «Exit», flashing light notifiers (strobe flashes);
sound — siren, special tinted signal;
speech — transmission of pre-programmed texts or broadcasting of dispatcher messages;
combined — combining several types of notifiers in one design.
Voice alarms or loudspeakers are also divided into electrodynamic, horn, electret, piezoelectric and others. Electrodynamic diffuser loudspeakers (wall, ceiling, sound columns) and horn loudspeakers are most often used in warning systems.
The number and power of loudspeakers are calculated based on the area of the room. In closed spaces, it is recommended to install ceiling or wall-mounted electrodynamic loudspeakers. For corridors and large open spaces, horn loudspeakers are mainly used due to the directionality of sound radiation. When designing a warning system, the general noise level typical for the room in which the loudspeakers are planned to be installed should be taken into account. It is recommended to select loudspeakers so that the sound pressure level they provide exceeds the general noise level in the room by 3–10 dB. Then the messages transmitted by the loudspeakers will be heard at the noise level. It should also be taken into account that in an emergency, the noise level in the room may increase significantly.
Design and Construction Features
The first two types of notification are usually not allocated as separate systems, but are designed on the basis of fire alarm or automatic fire extinguishing equipment. It is generally not difficult to control light and sound alarms or designate evacuation routes. Starting with the third type, notification is built as a separate system, usually according to a separate project.
When designing a system, attention should be paid to the method of delivering messages. It is believed that it is preferable to use a recorded message for broadcasting emergency messages, since an insufficiently restrained voice of the dispatcher can sow panic among people in the room. Psychologists also believe that announcements should be broadcast in a calm female voice, since its spectrum optimally matches the most important frequency range for perception (mother's voice). The text of an emergency message broadcast by the warning system in alarm mode should be neutral, aimed at suppressing panic. The texts of pre-recorded messages should contain information not only about the need for evacuation, but also about evacuation routes, direction of movement and other actions aimed at ensuring the safety of people. To attract attention to the message, some warning systems transmit a tone signal at the beginning and end of the message. In the case of using the warning system to broadcast music, radio programs or announcements, the volume of emergency messages should significantly exceed the volume of background messages. In addition, the warning system may include volume controls or program selectors in individual rooms. In this case, the building staff can stop the background broadcast if they wish. However, the warning system must necessarily include a relay for forced activation of full volume for emergency messages.
System Testing
Usually, the warning system is tested automatically after a specified period of time. During automatic testing of the warning system, a test pilot signal with a frequency of 20 kHz is added to the main signal. This signal is not perceived by the human ear; moreover, most loudspeakers in the fire warning system reproduce this frequency poorly. The operability of the amplifier is checked by the presence and amplitude of the pilot signal at the amplifier output. The integrity of the alarm loop in the system is monitored using a detector located next to the last alarm in this loop. Current detectors in the loudspeaker circuit monitor the operability of the loudspeaker itself.
The materials from the site soue.ru were used in preparing the article