Showing posts with label Photoelectric Smoke Detector.. Show all posts
Showing posts with label Photoelectric Smoke Detector.. Show all posts

Saturday, November 1, 2014

How Optical Smoke Alarms Work

How Optical Smoke Alarms Work

An optical smoke alarm (also called photo-electric smoke alarm) works using the light scatter principle. The alarm contains a pulsed Infra red LED which pulses a beam of light into the sensor chamber every 10 seconds to check for smoke particles.
When a fire breaks out smoke will enter the optical chamber through the opening vents. Smoke alarms from quality manufacturers have the chamber protected with insect screens to stop bugs entering and causing false alarms.
As the smoke enters the optical chamber, its particles cause the Infra red light to be scattered onto the photodiode light receptor.
Once the scattered light hits the photodiode light receptor a signal is sent to the integrated circuit which causes the alarm to sound alerting the occupants to the fire.

Wednesday, August 15, 2012

Smoke Alarm Maintenance

Smoke Alarm Maintenance

Smoke detectors are one of the most important safety devices you can install in your home to protect your personal belongings and your family. Once you've installed smoke detectors, it is absolutely necessary to test them regularly to ensure that they will sound during a fire. A great way to remember to change your smoke detector batteries in your home is to do so twice a year during Daylight Savings Time. When you reset your clocks forward or back, also change the batteries to keep your home and family safe!
You can keep your smoke alarm in its best condition using these tips.
  • Keep smoke alarms clean. Dust and debris can interfere with the alarm’s operation so vacuum over and around your smoke alarm regularly.
  • Once a month check the smoke alarm is working by pressing the test button. If you cannot reach the button easily, use a broom handle.
  • If all is OK you will hear a loud beep or a series of beeps. If you get no response it is most likely the batteries, or the alarm if it is a long-life type, will need to be replaced.
  • If a smoke alarm is not a long-life smoke alarm, its battery should be replaced every year. A good way to remember is to replace the battery at the same time every year, such as the beginning or end of daylight savings.
How long will my smoke alarms last?
You can expect your long-life smoke alarm to last for around 10 years. 
A smoke alarm is constantly monitoring the air in your home. At the end of 9 years after it has gone through over 3.5 million monitoring cycles, its components may become less reliable. As the detector gets older the chance it could fail to detect a fire increases. Smoke alarms that are wired into your electrical system (or burglar alarm) also need to replaced every 9 years.
Types of Smoke Detectors
When selecting a smoke detector, keep the following in mind: 
  • Photoelectric units are better for smoldering fires, such as electric fires in the walls, so they are ideal for kitchens and bathroom where these fires tend to occur. 
  • Ionization units give nearby air an electrical charge and then measure whether the charge stays constant or whether a fire is consuming oxygen in the air. These units are better suited to areas where fires get out of control, such as a basement near a furnace. 
Testing a Smoke Detector
To ensure that smoke detectors are working properly, test them on a regular basis. To do so:
  • Press the test button on the unit and wait for it to sound.
  • Light a candle and hold it six inches below the detector so the heated air will rise into the detector. 
  • If the alarm does not sound within 20 seconds, blow out the candle and let the smoke rise. 
  • If the alarm still does not sound, open the detector and clean the unit. Also make sure that all of the electrical connections are in good working order. 
  • Then, test the unit again. If it is still not working, replace it immediately.

To stop an alarm sounding you need to clear the air in the sensor chamber. Fan the alarm with a paper or tea towel is the best method to stop the alarm automatically. Don’t try to disable the alarm by removing the battery.