Humidity and nuisance alarms

Extending on from my recent blog on the Brisbane floods and the affect on fire & life safety, the uncanny summer weather in Melbourne has caused another problem.

The weather in Melbourne this summer has been quite tropical with a weather pattern extending form Far-North-Queensland all the way down to Tasmania.

This weather pattern has also led to a significant increase in the level of of relative humidity1 as reported by the Bureau of Meteorology. The relative humidity has been in excess of 85% for the period Jan 10 to Jan 13 which is significantly up on the average for this month to date, and the average over the past few years.

The consequences of humidity on fire detection systems

While these levels of humidity are not uncommon in Northern Australia (anything above 34° Latitude) in Victoria, the historic average for the summer months is about 60%.

As I said earlier the affect of the increased humidity has been a significant rise in the number of nuisance alarms associated with automatic fire alarm systems as reported on the 3AW Rumour File on Jan 14, 2011. Later in the morning, this report was commented on by Commander Ron Haines from the Metropolitan Fire Brigade - False Alarm Department.

Commander Haines also reported that during the preceding 24 hour period there were a total of 339 brigade calls, of which 258 or about 76.1% were from automatic fire alarm systems2. He went on to say that "a lot of them (false alarms) were due to moisture in the actual smoke detectors" and that "if an occupier does get a false alarm that they contact their maintenance company straight away...".

Difference between a smoke detector and a smoke alarm
For the sake of clarity, Automatic Fire Alarm Systems are generally designed to the Australian Standard AS1670.1 and use heat and smoke detectors manufactured to Australian Standard AS1603 and used in commercial applications.

Smoke Alarms on the other hand are generally designed to Australian Standard AS3786 and are used in residential applications.

You can read more about the differences between a smoke detector and a smoke alarm on another article I wrote some time ago.

Our observations

Our own system for tracking customer support requests for assistance also suggested there was an increase in cases logged due to environmental conditions. (we track about 18 root causes in 6 categories).

Personally I attended 6 calls all of which were directly related to the rise in humidity. Once case in particular left an entire retail precinct without mains power when the condensation from the air-conditioning system flooded a plant room.

What you can do

If you are responsible for an automatic fire alarm system in a commercial building there are 7 things you can do to help eliminate the risk of false alarm from water damage or an increase in humidity;

  • ensure sure your building is well ventilated
  • ensure your air-conditioning filters are clean and permit the free flow of air
  • ensure the drains from your air-conditioning systems are clear
  • never hose down (wash) your heat and smoke detectors
  • ensure your drain pipes are not blocked
  • repair any leaks in your roof
  • replace detectors that have previously caused a fault or alarm due to the ingress of water

In most cases you can eliminate root cause of a false alarm if you act on this simple list.

If you have been unlucky enough to have had the fire brigade attend a false alarm due to water damage, then you may be in a position to defend yourself against any fees levied against you provided you write to the MFB?s Alarm Assessment Services and can demonstrate a a reasonable excuse for the alarm being given3. Your letter should outline:

  • The actions taken to address the false alarm activation
  • Evidence of maintenance if the call was generated by an equipment fault. This information will greatly assist the Board in determining whether or not a charge will apply.

While I can't guarantee you will escape from the false alarm charges, you will have a pretty good case if you can demonstrate you have taken precautions to eliminate the root cause and have been proactive in your regular maintenance.

In the mean time, if you are experiencing ongoing false alarms feel free to post a comment below and we will try and answer your questions and steer you in the right direction to resolve your problems.


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smoke alarm problems
Submitted by Anonymous (not verified) on November 20, 2011 - 16:12.

Im an maintenance worker on an island along the great barrier reef and have had a long ongoing problem with smoke alarms on the resort.
We relpaced every alarm ( total of 30 ) with hard wired photoelectric alarms and with in two weeks have had a fair amount of them fail.

We have a verry hight ralitive humidty % ( up to 98% over summer months) and could really do with some advice on what would be the best product for us