Detecting and Alerting
Last week we talked about the steps that must take place to prevent a fire from occurring. By controlling the elements of the fire triangle, we can reduce the risk of fire. If a fire does occur in your facility, you must have a system to alert staff that they need to evacuate, as well as possibly calling the fire department. In Fire safety planning part 2 detecting and alerting, we will look at how a fire can be detected and staff can be alerted.
Fire watch is the most basic system that can be put into place to detect and alert staff of a fire. If you are doing hot work, a fire watch is required. A fire watch involves an employee watching to see if there are any signs of fire, such as smoke or flame. Before fire alarm systems common, the main method of fire detection was a night watchman who would basically be responsible for alerting the fire department in the event of a fire. Even today, if a fire alarm system is inoperable, a fire watch must be maintained until the automatic system is running again.
When a fire does occur, and there is no alarm system, a company must devise a way to alert staff. The internal public address system through the phone system is one method that can work, provided staff members know how to operate it. On construction sites, and other industrial sites where hot work is being performed, air horns are usually used.
When a fire watch is used, alerting the staff must be done in an effective way. On construction sites, the most common method is through the use of air horns. In other buildings, a public address system may be in place that could be used.
Fire Alarm System
Most buildings today have a fire alarm system that will have manual and automatic devises that are contacted to a central panel that will in turn activate an audible device and call the fire department. Some of the alarm devices may also trigger a fire suppression system, such as sprinkler. Fire detection devices can be connected to a security system or to a separate panel that is made for this purpose.
The components of a fire alarm system are:
Pull Stations– Pull stations are manual devices that an individual can use to activate the alarm system. They are usually located by exit doors and are recognized by their red colour. Always know where the pull stations are located and ensure they are never blocked by shelves, tables or merchandise that can block access or even hide it from view. Retail businesses have a nasty habit of doing this. The two most basic components of a fire alarm system in Canada are a pull station and a bell.
Smoke Detectors– As the name suggests, smoke detectors will detect the smoke from a fire. There are two main types typically used: photoelectric and ionization. Before doing any work that can cause dust or fumes, check to see if any smoke detectors are in the area. It may be necessary to cover the detector to prevent it from false alarming. Know where the pull stations are located in the event of an actual fire. There is another type of smoke detector called a beam detectors that s used to cover a large area. Two devices send a beam between them and will activate when particulate matter passes between the beams.
Heat Detectors– Heat detectors sense any increase in temperature in their area. There are two types: fixed temperature, which activate when the heat exceeds a certain limit, and rate of rise, which will activate if the temperature goes up faster than normal. Heat detectors are less effective than smoke detectors but there are some areas, such as workshops and garages, where the smoke detector would be false alarming if it was used there. Sprinkler heads also activate when there is an increase in temperature. All heat detectors have a disc on them and when doing maintenance, it is important to note that the discs are not damaged in any way. It is also important to not have any paint on a heat detector, as this impacts the effectiveness of the detector.
Audible/Visual Devices– Once a system has been activated, it there will need to be a noise of some type used to get all personnel out of the building. Bells, horns, klaxon sirens have all been used depending on the size of the building and the amount of noise that exists under normal circumstances. Bells are the most common, although small horns are used that have a strobe feature. Klaxon horns or sirens would be used in industrial settings so they can be heard above the noise. Visual devices, such as strobe lights, are used in both industrial settings and in cases where a hearing impaired person is around. Some building, such as hospitals, can have speaker systems that will allow someone to make an announcement about the emergency situation.
Fire Alarm Panel– a fire alarm panel not only monitors and controls the above devices, but also the sprinkler and other fire suppression systems in most buildings, alert the fire department, close fire doors and smoke shutters that are usually left open, deactivate the ventilation system to prevent more air from getting to the fire and smoke from spreading throughout the building, and recall the elevators to the ground floor (or second floor if the fire is on the ground floor). Fire alarms panels can be hardwire (where the devices on one circuit are only shown as a light on the panel) or addressable (each device location, and type, is given on a display screen).The size of the building you’re in will determine the size and type of panel you need.
You need to have a system of some type in place to detect fires and alert staff. Whether it is the personnel doing a fire watch or an electrical system, your system needs to be known by staff and tested at least once a year. I spent eight years working for a fire alarm company as a technician’s assistant in various buildings and industries. The system you have in place must work with the conditions in the building. When designing such a system, the Canada Building Code and the Canada Fire Code provides benchmarks. Fire safety planning part 2 just touches the surface of what you need. Next week, we will talk about what we can do to suppress the fire.