Ensuring intrinsic fire safety in explosive environments
Product support team leader at Hochiki Europe, Simon Massey, explains what installers should take into account when recommending fire safety equipment for explosive atmospheres to ensure businesses comply with legislation and uphold the safety of workers.
Hazardous areas are an unavoidable feature of buildings across a host of industries, from petrochemicals premises, to food manufacturing facilities. Such environments not only need fire safety systems capable of alerting people to an emergency as quickly as possible, but also contribute to reducing the risk of a fire by eliminating potential sources of ignition. This is crucial both to uphold the safety of building occupants and to comply with legislation, including the Dangerous Substances and Explosive Atmospheres Regulations 2002 (DSEAR).
Under DSEAR – recently updated to incorporate the Classification, Labelling and Packaging of Chemicals Regulations 2015 (CLP) – employers must assess the hazards posed by any dangerous materials on their premises, and take steps to minimise the risk to worker safety. These regulations also require the identification of any hazardous areas in the workplace – defined in DSEAR as a “place where an explosive atmosphere may occur in quantities such as to require special precautions to protect the safety of workers”.
Such environments can be the result of gases or dust present in various quantities in the air that can be ignited by an electrical spark or open flame. The standard EN60079-10-1 categorises these hazardous areas into zones according to the nature of the explosive material and the amount of time it remains in the atmosphere:
- Zone 0 – where explosive gas is continuously present in the atmosphere for long periods
- Zone 1 – where such gas is likely to occur in normal operation
- Zone 2 – where gas is not likely to be present in normal circumstances and, if it does occur, will only exist for a short time
- Zone 20 – where airborne combustible dust is present continuously or for long periods
- Zone 21 – where such dust clouds are likely to occur in day-to-day operation
- Zone 22 – where dust is unlikely to be present but, if it occurs, will only persist for a short period.
To minimise the risk of ignition in the hazardous areas of a business’s premises, specialist “intrinsically safe” fire safety solutions appropriate to the space’s zone category must be selected by installers.
But what do installers need to know to ensure they recommend the right equipment? And what do we mean by intrinsic safety?
Choosing the right technology
To ensure that the life safety system selected for the hazardous area in question is compliant with DSEAR, installers need to be sure it is appropriate for the space’s zone classification. Under the regulations, only Category 1 products are suitable for use in rooms classified as Zone 0 or 20, but Zones 1 and 21 can be equipped with either Category 1 or 2 technology. Zones 2 and 22, however, can be fitted with Category 1, 2 or 3 rated systems.
What all life safety system categories have in common, however, is that they must be ‘intrinsically safe’. Such devices differ from standard technologies in a number of ways. While, aesthetically, both types of product can be similar in shape and size, intrinsically safe products have to have additional warning information printed on their casing – including details about the zones for which they are suitable.
Most importantly though, is the technology used inside. Fire safety equipment installed in a hazardous environment must operate using the lowest possible power levels to minimise the risk of excess thermal energy or an electrical spark that could ignite the flammable material in the atmosphere. As a result of this low power requirement, many intrinsically safe devices are non-pulsing, meaning that their LEDs will not flash when polled.
The low power requirement of intrinsically safe fire safety systems also distinguishes them from flameproof devices. Flameproof solutions are mainly high power devices that feature a specially developed casing designed to contain an internal explosion without transmitting it outside the box. This casing is also insulated to ensure its external surface remains cool enough to prevent the ignition of the explosive atmosphere outside.
However, due to their high power requirement, many flameproof solutions are not intrinsically safe. Such solutions can be used in areas classified as Zone 1, 21, 2 and 22, as long as flameproof wiring is used to minimise the risk of ignition, but they cannot be used in Zones 0 or 20. Low powered intrinsically safe products, on the other hand, are not at any risk of an internal explosion. This means they don’t require a flameproof casing and are safe for use in all hazardous areas.
Systems for high-risk industries
Installers considering fire safety technology for high-risk industries should ensure that their shortlisted products are compliant with ATEX Directive 94/9/EC, as well as EU Construction Products Regulation 305/2011. In addition to these though, installers should also be aware of the difference between intrinsically safe life safety systems and other key certifications to ensure they select the right solutions for their needs.
For example, ‘Safety Integrity Level’ (SIL) approved products are not the same as intrinsically safe devices. The latter are certified for general use in high risk industries, such as the petrochemical and transport sectors. Intrinsically safe solutions, on the other hand, are for use specifically in hazardous areas.
The International Electro-technical Commission (IEC) has also published standards for safety performance for hazardous operations, including the IEC 61508 Functional Safety of Electrical Safety-Related Systems and the IEC 61511 Safety Instrumented Systems for the Process Industry Sector. These certifications – which have been widely adopted in the hydrocarbon and petrochemical industries in recent years – require the use of SIL-approved products for compliance.
To help installers comply with these and similar safety standards for high-risk industries, while minimising explosive risk in hazardous areas, there are fire safety technologies available on the market now that are both SIL-approved and certified to be intrinsically safe. Installers should look out for approval to both certifications when making their selection.
To ensure optimal safety in explosive environments, it is not enough for installers to simply fit intrinsically safe devices. There are also a number of other precautions when linking the products to the rest of the life safety network to maximise safety for building users.
A key issue that installers to be aware of is that not every space in a building is a hazardous area – most rooms in any property can be classified as ‘safe’, which means that they can be fitted with standard life safety devices.
To streamline maintenance and operation for facilities managers in such buildings, installers should consider fitting intrinsically safe compatible control modules. These provide a safe interface between the high-power standard and low-power intrinsically safe systems to allow authorised personnel to set up and control both networks from a single convenient location. They also provide line monitoring for open or short circuits in the wiring connected to both networks to minimise the risk of a high-voltage current running into the hazardous area.
While intrinsically safe compatible modules can enhance convenience for building owners, they cannot on their own lower the current to a level suitable for hazardous areas. With this in mind, it is crucial that installers select an intrinsically safe barrier, which will actively reduce the power in electrical wiring to a safe level. Both the barrier and the module must be installed in one of the designated safe zones in the building to ensure no high power levels are experienced in the hazardous area.
Finally, to optimise safety, all devices fitted in a hazardous area should be installed using intrinsically safe mounting bases. These provide a further barrier to any high current and minimise the risk of electrical arcing leading to a spark that could ignite an explosive atmosphere.
Taking such precautions during installation can ensure that the fire safety system is compliant with the requirements of intrinsic safety and offers minimal fire risk even in the most hazardous environments.
Key to intrinsic safety
By recommending and fitting the right life safety equipment for the needs of the space in question, installers can ensure they have taken every step to support building owners to achieve their high safety goals. In doing so, they can help safeguard both their premises and their workers from the threat of an explosive fire.
If installers require guidance when choosing the right intrinsically safe products, or fitting them correctly, there is plenty of advice available from the manufacturers of fire safety systems.
For more information, go to www.hochikieurope.com/is