Smoke Alarms - Everything You Need To Know

Posted by George eames on

Smoke Alarm

The smoke alarms in your house are absolutely vital, they save lives. Please before we go any further if you know there maybe an issue with your smoke alarms get it resolved. According to the NFPA (National Fire Protection Association) having a working smoke alarm in your home cuts the risk of you dying in a fire by 60%.

Smoke alarms detect fires by sensing small particles in the air in your home using a couple of different kinds of technologies. Once they detect those particles and the levels go above a certain threshold, they signal the alarm to sound so that you and your family can get to safety and call the fire brigade.

The two common technologies used within some detectors are as follows:

  • Ionization Detectors -  They use a small piece of safely shielded radioactive material that ionizes (electrically charges) the air molecules between two metal plates. When smoke is detected it enters the alarm and once the level of particles enters a specific amount the device will register this as a threat, which will set off the alarm. An example of this will be Aico's E141RC.
  • Photo Electric - These types are less common but are available. This technology works by detecting light that is reflected off particles from a light beam inside the sensing chamber. When no particles are present in the sensing chamber, the light from the beam does not strike the light detector, indicating all clear. When there are particles present and the amount of light registered by the light detector reaches a certain threshold level, the alarm sounds.  Please see example here!

Both type of technologies are effective and will detect slow burning (smoldering) fires and also fast burning fires. Both technologies have their different strengths too. Ionisation alarms detect small black soot particles from quickly burning fires more easily. This is because the particles are produced more quickly in a fast burning fire. Photo electric alarms are slightly better at detecting smoldering fires due to them picking up the reflective particles in a slow burning fire.

There is a common term used for smoke alarms and that is 'nuisance alarm'. This is when an alarm is so sensitive that it picks up slightly burned toast or your delicious sunday breakfast. People often complain about their alarms being so sensitive but in reality you'd prefer your smoke alarm to be sensitive than unresponsive. 

Due to the nature of the times we are living in and technology always advancing, researches are continuously trying to improve the functions of smoke alarms and I am sure one day in the near distant future we will have smoke alarms that can detect a fire and understand when your bacon is slighlty over cooked... one day!

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