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Smoke alarms

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Why do you need a smoke alarm?

  • More than half of all fire deaths occur in homes, mainly while people are sleeping.
  • You can't rely on your senses to detect a fire while you are sleeping - but a smoke alarm gives that vital early warning.
  • Sound is the best way to wake a person from a deep sleep.

How do they work?

  • Smoke alarms detect smoke before you can even see or smell it.
  • The smoke particles break a circuit in the smoke detector which triggers a loud warning signal, and keeps sounding until the smoke clears.

Where should I put smoke alarms?

  • Smoke rises and moves along the ceiling, it will move up stairwells and vertical openings.
  • When it can't rise anymore it will build up, working its way down again.
  • So it is important to place the smoke detectors on the ceiling to get the earliest warning. If you must position it on the wall put it 100mm away from the ceiling due to dead air pockets.
  • Fit a smoke alarm to every bedroom plus the lounge and hallways. If finance is limited the most important areas to cover are the hallways near the bedrooms (leave the doors open) then install in each bedroom as finance allows, as soon as possible.
  • Don't put them in the kitchen, garage or bathrooms unless they are specially designed smoke alarms for those areas. Heat detectors are available for the kitchen

Does the smoke alarm require maintenance?

  • Yes, dust and spider webs can effect the alarm.
  • Clean with the vacuum cleaner once a month.
  • Test the alarm once a month by pushing the test button in.
  • Change the battery once a year (such as on New Years day day light saving or a family members birthday)
  • All smoke alarms will sound a short "beep" every so often indicating that the battery is going flat.

Will any smoke detector do?

  • The Fire Service recommends only those smoke detectors which have certification.
  • Check the packaging to make sure you are buying an alarm with a recommended standards symbol displayed.

What is available for people that are deaf or have hearing loss?

  • The are two types of models available. One has an extra loud alarm and the other has a strobe flashing light and sound.

Should I replace my smoke alarm?

  • Smoke alarms that are ten years old are near the end of their service life and should be replaced. A smoke alarm constantly monitors the air 24 hours a day. At the end of 10 years, it has gone through over 3.5 million monitoring cycles. After this much use, components may become less reliable. This means that as the detector gets older, the potential of failing to detect a fire increases. Replacing them after 10 years reduces this possibility.

My smoke alarms are wired into my electrical system (or Burglar Alarm). Do I still need to replace them every ten years?

  • Yes. Both types of alarms are affected by age.

Is there more than one type of smoke alarm and what is the difference?

  • One type is called and ionization alarm because it monitors the 'ions', or electrically charged particles. Smoke particles enter the sensig chamber change the electrical balance of the air. The alarms horn will sound when the change in the electrical balance reaches a certain level.
  • The other type is of alarm is called photo electric because its sensing chamber uses a beam of light and a light sensor.
  • Smoke particles entering the chamber change the amount of light that reaches the sensor. The alarm sounds when the smoke density reaches a preset level.
  • Note: BRANZ recommends photo-electric type smoke alarms in the living area and Ionization type smoke alarms in the hall and bedrooms.

Is one type better than the other?

  • The ionization alarm responds faster to small smoke particles, while the photoelectric responds faster to larger smoke particles. As a rule of the thumb, fast flaming fires produce smaller smoke particles and smoldering fires produce large particles. Thus the response time of the two alarms will vary, depending on the mixture of small and large particles from the fire. But test results show that the difference in response times are small enough that both types provide enough time to escape.

What is more important, the smoke alarm type or the number?

  • The number of detectors is more important than the type.
  • Installing several smoke detectors of each type will provide better coverage in the extreme case of long-term smoldering or fast flaming fires. But since both alarms respond in time to escape, the most important thing is to install enough alarms in the correct locations. Detectors are available with both types of sensors in the same unit, but if the choices are between having only one of each type or having more of the same type, more is the better choice.

My smoke alarm goes off when I cook, how can I stop this?

  • If a alarm regularly responds to smoke from cooking there are several options to handle this problem. One way is to replace the alarm with one that has a button to silence it for a few minutes.
  • Another way is to move the alarm further away, giving the smoke more time to dissipate.
  • If the detector is the ionization type, another option is to replace it with a photelectric. This detector is less sensitive to the smaller particles so is less affected by cooking smoke or use a heat detector.
  • To stop an alarm sounding you need to clear the air in the sensor chamber. Fanning the alarm with a paper or tea towel is the best method and the alarm will stop automatically. Do not try and disable the alarm by removing the battery.
  • Call your local fire station for advice on where to install the smoke alarms, and assistance with installation for the elderly and people with disabilities.

 

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