Fire Alarm -- Description
What is a Four Wire Smoke Detector?
-- A 4-wire smoke detector is just like a 2-wire smoke detector, except that it receives its power from an auxiliary power supply rather than the conventional Initiating Device Circuit. Both the 4-wire and the 2-wire smoke detector sense particles in the air and call the particles smoke... Read More
NFPA's 7 Classes of Fire Alarm Paths
-- The NFPA has divided the signal paths in a fire alarm system into 7 classifications: Class A, Class B, Class C, Class D, Class E, Class N, Class X. These classifications don't show how to wire up anything, these classifications show what happens when things go wrong... Read More
What are the Signals on the SLC?
-- I would like to know what type of signal is there between addressable fire detectors and the fire alarm monitoring panel. Actually I want to know how the address / location of... Read More
What's the Difference Between Class A and Class B?
-- The Fire Alarm System is a Life Safety System - so the occupants of a building can escape quickly, the idea behind a Fire Alarm System is that it will provide a warning that there is a fire. The trouble is, if something is wrong with the system, like a wire is broken somewhere in the building, the Fire Alarm System... Read More
Why Doesn't a Smoke Detector Always Detect?
-- The NFPA wants smoke detectors tested in place to make sure smoke enters the smoke chamber. Keep in mind that a smoke detector can't detect smoke that doesn't get to the detector. When a smoke detector doesn't... Read More
Firefighter Don't Reset the False Alarm
-- When the alarm sounds and the firefighter arrives, even for a false alarm, the firefighter is on site for property protection and life safety. So when leaving, from the point of view of the firefighter, the ... Read More
Why reverse polarity for fire alarm horns?
-- A fire horn is turned like a light; it turns on when power is applied and turns off when power is removed. But then again, to constantly check continuity of the wires (supervise the wires), the Fire Alarm Control Panel (FACP) always has power applied to the circuit. Read More
What is a Fire Alarm Zone?
-- Building zones aren't determined by where the wires are run for the fire alarm system, building zones are determined by the building's fire-control -- fire-fighting divisions and by the building's smoke-control divisions... Read More
What Is Fire Alarm Trouble Power?
-- In the "Old School" type of fire alarm system, before the smoke detector was invented, even though the fire alarm systems used AC, all voltages were in a steady state: either on or off. Until someone ... Read More
If It's There -- It Has To Work
-- Whether its smoke detectors on the ceiling or the firefighter's telephone system, people think that if it's there, it's real and it works. Sometimes, people even stake their lives on that device or system ... Read More
What is a 4 Wire Smoke Detector?
-- Even though it uses an internal protection resistor and internal alarm relay contacts, a 4 wire smoke detector is basically a 2 wire smoke detector; it detects smoke and sends an alarm ... Read More
What Makes a False Alarm so Dangerous?
-- Each false fire alarm increases the severity of a real fire. The increased severity from false alarms comes from the greater chance of loss of life or a greater chance of injury. This is a progression - with no false... Read More
What is an Area of Refuge?
-- You hear the message "Use the Stairs, "you see the sign "In case of fire, don't take the elevator." To get out of the building from the higher floors, when the building is on fire, the stairs ... Read More