Security & Fire Protection Systems/Heat Detectors - False Alarms

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Question
Hi
would you be able to tell me what can cause false alarms in heat detectors (such as insects or dust).  Can electtrical interference cause a false alarm in heat detectors?

Thanks

Answer
Firstly, let's understand what a heat detector is and how it works.

Electronic Heat Detectors are powered by the fire protection panel, or CIE. They operate by measuring air temperature and are slower, in comparison to other detection methods, in detecting a fire alarm condition and should be used in conjunction with other fire protection devices, such as Smoke Detectors.

There are two main types of heat detectors:

Fixed Temperature Heat Detectors

As the name suggests, these heat detectors are designed to go into alarm at a fixed temperature. A fixed heat detector could be used in areas where air temperature changes dramatically without a fire condition being present and come in many temperature settings.

Fixed heat detectors are usually installed in non residential settings. As an example, a fixed heat detector would be the appropriate kind of detector for a large commercial kitchen area  as they are prone to rapid temperature changes and a rate of rise detector would generate a false alarm.

Rate of Rise Heat Detectors

Rate of Rise heat detectors are triggered by rapid changes in air temperature.

A fuel fed fire would best be detected by a rate of rise heat detector.  These rate of rise detectors are designed to go into a alarm when the air temperature rises faster than a normal condition would permit. For example, a rate of rise heat detector is best suited for areas where combustible fuels are present (i.e. Garages, wood stores, paint facilities, etc.)

When properly installed, heat detectors will respond only when a fire is well-established and generating a high heat output.

So, to answer the question, dust or insects can NOT trigger a false alarm with a heat detector, nor usually electrical interference (although there is the small posibility). The most common causes of false alarms with heat detectors are:

1) Improper Installation
2) A change in the environment
3) Mechanical issue (i.e. the unit is failing or has failed)
4) A combination of one or more of the above

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Malcolm Evans

Expertise

I can answer questions relating to Fire systems and Gaseous Fire Suppression systems, both mechanical (including Integrity Testing) and electrical components (Addressable and Conventional systems) and can cover UK standards and regulations. Also, I am Ansul trained and certified in R-102 Ansul Kitchen Suppression system design, installation and maintenance.

Experience

I have 2 years experience with my current employer, a UK Fire Protection Company, in installation, testing and maintenance of various system types, and design of Ansul R-102 Kitchen Suppression systems.

Organizations
FIA (Fire Industry Association) and BAFE (British Approvals for Fire Equipment) accredited. Ansul certified.

Education/Credentials
Secondary Education (GCSE's) and Technical College (City & Guilds).

Past/Present Clients
Land Rover; RBoS; Wilkinsons; Jaguar; British Telecoms; British Sky Broadcasting; Welsh Assembly; BBC Scotland; Crowne Plaza Hotel chain; Holiday Inn Hotel chain; Hilton Hotel chain; London Heathrow; Gatwick; Financial Institutions; Local Government Offices and many more

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