Before recommending a heat detector for a fire suppression project, we always consider three safety factors. We start by asking our customer:

1. Will the detector be installed in a hazardous area where there is an explosion risk?
2. Does the air around the detector contain any aggressive or corrosive substances?
3. Is additional protection required from possible water ingress? 

In hazardous areas, safety measures are required to isolate the electrical components, which connect the detector to the alarm system, and prevent any spark from causing a potential explosion. 

In safe or hazardous areas, the detector may need to be protected externally from physical or chemical damage caused by its environment, which could hamper its reliable operation during a fire.  

An area is defined as hazardous whenever there is a possibility that flammable gas or dust could build up in a confined space. In sufficiently high concentrations, combustible materials can create conditions where an electrical spark or high temperature is enough to ignite a volatile atmosphere. The resulting explosion will have serious consequences, especially in locations like oil platforms.

ATEX (or Ex) is a European certification given to equipment that has been tested and approved as being ‘intrinsically safe’. This means an ATEX-approved product has demonstrated that it can be used safely in a hazardous or explosive atmosphere. There are two European Directives in place regarding the control of explosive atmospheres, commonly known as ATEX 153 and ATEX 114. 

Any heat detector lacking ATEX approval should be assumed to be capable of causing a spark - and must not be brought into any area considered as an explosive atmosphere.

There are different kinds of combustible material covered by the ATEX guidance. Examples of hazardous environments include gas and petrochemical plants, paint and chemical factories, paint spray booths, stores of flammable materials, turbine rooms, extract ductwork and workplaces which handle fine organic dusts, such as grain flour or wood. 

The heat detectors we supply from Fenwal Controls are hermetically-sealed mechanical devices. They are designed to activate at a given set point, passing an electrical current through a simple switch which sends a signal to the alarm or fire suppression system. 

Because it is hermetically sealed and a mechanical device, the heat detector itself is intrinsically safe by design for use in a hazardous environment. However, to isolate the electrical connection to the corresponding alarm system, an ATEX-approved housing must be used in any hazardous environment. 

Depending on the application, further modifications to the enclosure may be required. These are recorded on the label that is provided on the finished housing. 

This might include details of the specific international certification and approval type. Other options include the temperature setting, any optional features, and the finished coating of the enclosure. 

Normally, an unpainted housing will be neutral or grey. It will be coloured if a special paint has been applied for protection in an aggressive environment. However, custom colours can also be applied if the detector needs to be identified as part of a hazardous area or a particular area of a facility. 

Additional labelling might also be required, for HSE approvals for example, either at the factory or added by the installation engineer to the standard product label. If traceability is required, an additional sticky label or loose tag with an identification number can be specified when ordered.

Heat detectors are sometimes used environments that can be damaging or corrosive to the exterior shell of the detector. Any damage to the detector can prevent it from operating correctly – and a damaged or corroded fire detector should always be replaced immediately. In such aggressive environments, a detector should be specified that is made from a special alloy or treated with a protective coating. 

• In marine environments, there are high levels of salt in the air, which can corrode standard grade stainless steel. This can damage the internal contacts and reduce the lifespan of the detector. Any corroded detector should be replaced immediately.  In such applications, a marine-grade, corrosion-resistant alloy should be chosen for the detector. Marine-grade detectors are specified for use on oil and gas offshore platforms but they are also of benefit in waste treatment plants, chemical plants and power plants where there are high levels of corrosive chemicals like toxins, acids or diesel. 
  
  
• When fire detectors are used in spray booths, there are two further problems to consider. Paint contains acetone and this can attack the stainless steel body of the detector over time. Furthermore, any coating of paint on the shell of the detector will slow down its response time. The solution is to apply a special fluorocarbon protective coating to the detector. This coating will resist the paint, making it easy to keep the detector clean.

Finally, a heat detector can be damaged in two further ways, which might affect its safe operation.
Detectors exposed to wet weather, or used in an area with water, mist or spray, should be protected from water ingress using a weather-proof IP66-rated box. This will prevent erratic readings from the moisture or possible corrosion of the electrical connections over time. 

Detectors can also be accidently hit or knocked by vehicles or equipment. Any physical impact might damage the internal contacts inside the detector and the detector should be replaced immediately. This kind of damage can be prevented by adding a simple guard or protective tube around the fire detector.