Working smoke detectors or smoke alarms greatly decrease the risk of injury or death in a fire. Like any Life Safety device, smoke detectors and alarms need to be inspected, tested and replaced on a regular schedule to ensure they work effectively.
Smoke Alarms and Smoke Detectors
As we discussed in our blog Smoke Alarms, there is a difference between a smoke alarm and a smoke detector. A smoke alarm is a stand-alone device with a built-in sounder, a power supply, and a sensor. A smoke alarm is not connected to a fire alarm control panel, but may interconnect with other smoke alarms within the building. A smoke detector is part of a commercial fire protection system, it has only a built-in sensor and sends information to the fire alarm panel.
However, the sensing technology within smoke alarms and smoke detectors are the same – primarily, photoelectric smoke detection. This sensing system can become less responsive as it ages. To ensure your people and assets are protected, you should replace all smoke detectors and smoke alarms when they are 10 years old. To determine the age of your alarm/detector, look at the back where you will find the date of manufacture.
You should test your smoke alarms once a month by pushing the test button. Twice a year you should replace the batteries in all of your smoke alarms, it is encouraged that you do this when your clocks change for daylight savings as it serves as a regular reminder. You can clean your smoke alarms by vacuuming the outside, do not remove the alarm’s cover to vacuum.
Smoke detectors will be professionally inspected on an annual basis when your fire alarm system is inspected and tested. Your Life Safety Partner will check for the proper signal reception from the detectors at the alarm panel, clean your smoke detectors, and, when required, perform a sensitivity test.
Active vs Passive Smoke Detection
Air sampling smoke detectors are “active” systems which constantly sample the air from multiple points throughout the environment. Other smoke detection devices are “passive” systems. They rely on the heat of the smoke and the airflow of the room, for the smoke or heat to reach the detector. This can be a problem in rooms with constant air flows like server rooms, with smoldering fires which generate relatively little smoke, and with incipient stage fires where the smoke is not hot and therefore has very little thermal lift. Since these environmental conditions are particularly prevalent in server rooms, this is one space where air sampling smoke detectors are best used.
Server Room Fire Prevention with Air Sampling Smoke Detectors
Air sampling smoke detectors are classified as Very Early Warning Smoke Detectors (VEWSD). This is especially important in server rooms where the incipient stage of an electrical fire may not be detected by EWSD (Early Warning Smoke Detectors). This stage, which can last for hours or even days, is not a visible fire but the human nose may smell the fumes.
Smoke from a server room fire is harmful to other electrical equipment in the space. The by-products of smoke from PVC and digital circuit boards are gases such as HCL, and these gases will cause corrosion of IT equipment. Even at very low levels, the gas can cause moderate corrosion with long-term effects on electronics.
Air sampling smoke detectors can detect smoke at this incipient stage to activate alarms so that a response can be taken (whether through a fire suppression system or by an individual trained to respond) to put out and address the cause of the fire. Because the system monitors the space for overheating materials, and can detect this even before an actual fire develops, air sampling detectors act as a fire prevention tool.
How Air Sampling Smoke Detection Works
Air sampling smoke detectors are quite different from conventional spot type smoke detectors. Aspirating systems are typically made up of a number of small-bore pipes laid out above or below a ceiling in parallel runs, some feet apart. Small holes, also some meters apart, are drilled into each pipe to form a matrix of holes which are the sampling points, providing an even distribution across the ceiling. Air or smoke is drawn into the pipework through the holes and onward to a very sensitive smoke detector mounted nearby, using the negative pressure of an aspirator (air pump).
While air sampling smoke detectors are more sensitive to detecting smoke, they are less susceptible to the major sources of false alarms – dust, draughts and electrical interference. False alarms are a definite annoyance to building owners, managers and tenants. They also have a higher cost for our fire service providers, click here to read about the true cost of false alarms.
Sensitivity Settings of Air Sampling Smoke Detection Systems
Aspirating Smoke Detectors can have the sensitivity settings for alarm levels adjusted. The levels are typically set for an Alert, Action, and Fire 1. An Alert sends notice to local staff so they can investigate the threat of fire that has been detected. The Action level is generally used to initiate smoke control, begin a warning sequence via the evacuation system, and alert further staff members to the situation. The Fire 1 alarm indicates a fire condition is very close or has started. This alarm would activate evacuation procedures for the building, the fire alarm panel for the affected zone is activated, notifying the monitoring company and fire services. An additional Fire 2 threshold can be set; this level would act as confirmation of a serious fire event with the option to activate a suppression system. This should be a safety net setting, as the building’s fire systems and procedures should have operated properly before this point to prevent the fire.
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Widespread use of smoke alarms began in the 1970s, and have greatly reduced the number of home fire deaths. Prior to the 1970s, the average number of annual deaths by home fires was roughly 6,000. While there has been a dramatic decrease in home fire deaths, there is still more work to be done. Three out of every five home fire deaths occur in a home with no smoke alarms or no working smoke alarms. No smoke alarms were present in more than 1/3 of home fire deaths. In reported home fires where smoke alarms were present, but did not operate, almost half of the smoke alarms had missing or disconnected batteries. A quarter of the smoke alarm failures were due to dead batteries. NFPA estimates that there are about five million homes nationwide without smoke alarms.
In 2015, 3,280 civilians died in fires. Most fire deaths are not caused by burns, but by smoke inhalation. An individual can become incapacitated by smoke so quickly that they are overcome and can’t make it to an otherwise accessible exit. Having smoke detectors and alarms in your home and business can provide valuable time to evacuate, preventing injury and death.
A smoke alarm is a stand-alone device with a built-in sounder, a power supply, and a sensor. A smoke alarm is not connected to a fire alarm control panel, but may interconnect with other smoke alarms within the building. A smoke detector is part of a commercial fire protection system, it has only a built-in sensor and sends information to the fire alarm panel.
There are two main types of smoke detection technology used both in stand-alone devices and as the sensor in smoke alarms, ionization and photoelectric. Each has advantages, for best protection you should use both types of smoke detection technologies. There are units available which utilize both technologies in a single device for both detectors and alarms.
Ionization Smoke Detection
Ionization Smoke Detectors are generally more responsive to fires that have flames. The detectors have a small amount of radioactive material between two electrically charged plates, this ionizes the air and causes current to flow between the plates. When smoke enters the chamber, it disrupts the flow of ions thus reducing the flow of current and activating the alarm.
Photoelectric Smoke Detection
Photoelectric Smoke Detectors are more responsive to fires that begin with a long period of smoldering. Photoelectric-type detectors aim a light source into a sensing chamber at an angle away from the sensor. When smoke enters the chamber, it reflects the light onto the light sensor which triggers the alarm.
Smoke detectors have advanced technologically to be more user friendly. In addition to combination detectors which include both photoelectric and ionization technology, you can also get detectors that combine CO detection, or many have features for silencing nuisance alarms. Smoke alarms can be interconnected to allow an alarm to sound throughout the house or building when one unit detects smoke; some of these devices can be programmed to provide audio messages that state for which room the alarm has sounded.