Understanding hazardous area classification

Although every responsible business works to eliminate risk, there are some industries where dangers are ever-present. Workplaces in which explosive atmospheres occur are among the most challenging of these. They include the oil and gas industry, certain chemical industries, and even the food and beverage industry. 

Hazardous area classification indicates workplace areas where there’s a risk of explosion from flammable gases, vapours, or dust. In areas such as these, the tiniest spark can set off explosions or raging fires. If this were to happen, there would be a high risk of serious injuries, death, and destruction of property. 

Of course, some areas are more hazardous than others, and this is indicated by hazardous area classification. They’re based on Dangerous Substances and Explosive (DSEAR) regulations and indicate the level of safety precautions that must be taken. 

What are the hazardous area classifications?

The UK’s Health and Safety Executive (HSE) recognises three types of hazardous areas where explosive gases may be present: hazardous area classification zones 0, 1 & 2

• Zone 0: Explosive atmospheres are continuously present or are present for long periods. 
• Zone 1: Explosive atmospheres are likely to be present during normal operation. 
• Zone 2: Explosive atmospheres can develop, but are unlikely to do so. When they do occur, they will rapidly dissipate. 

Explosive dust hazardous area classification is designated by Zones 20 to 22.  

• Once again, the lowest figure, Zone 20, indicates the highest level of risk: one that is continuous or near continuous. 
• Zone 21 designations mean that explosive dusts are likely to be present during the course of normal operations.  
• Zone 22 indicates a low likelihood of explosive atmospheres and a high probability that they will quickly dissipate. 

Origins of hazardous area classification 

The dangers of the coal mining industry ultimately led to hazardous area classification. Methane explosions were once a common workplace risk in coal mines, and coal dust explosions could be equally fatal. 

Early interventions included sending “firemen” wrapped in wet blankets into mines ahead of workers. Their task was to deliberately ignite hazardous atmospheres, and their careers were often short-lived. Later, mining engineers discovered that improved ventilation could reduce risks, and various steps were taken to reduce ignition hazards. 

As is too often the case, precautions to be taken in hazardous atmospheres were only developed in the wake of catastrophic accidents in which lives were lost. Today, regulations require employees to implement every possible measure to prevent the ignition of hazardous atmospheres, and risk mitigation forms part of employers’ legal compliance duties. 

ATEX standard for hazardous area classification

ATEX stands for “Atmospheres Explosibles,” and consists of regulations that apply throughout the European Union. Atmospheres are classified into zones as described above, and equipment for use in these zones is standardised across the UK and the EU under ATEX regulations. 

Certified equipment carries a conformity mark indicating the type of hazardous area for which it is deemed safe. We can therefore say that ATEX is a component of DSEAR that allows companies to source compliant equipment across borders. 

Equipment for hazardous areas 

Intrinsic safety (IS)

Intrinsically safe equipment is designed with highly explosive atmospheres in mind. It is used in Zones 0 and 1. This equipment will not give off enough energy to act as a source of ignition. 

Explosion / flame proof (Ex d)

Any equipment that may explode if it malfunctions presents an unacceptable level of risk when used in areas where explosive atmospheres are present. Explosion proof devices will not explode or give off heat and sparks in the event of a malfunction. They are generally used in Zones 1 and 2 and are not used in the presence of hazardous dust. 

Increased safety (Ex e)

The equipment is designed to eliminate any potential for giving off heat or sparks that may serve as a source of ignition. These devices are used in Zones 1 and 2 or 21 and 22.

Encapsulation (Ex m)

Components are sealed (encapsulated) using a material that will prevent it from acting as a source of ignition. Because its safety depends on being sealed, the encapsulation must remain intact if it is subjected to impacts or other forms of mechanical damage and must withstand harsh environments. These devices are suitable for use in Zones 2 and 22. 

Purged and pressurised equipment (Ex p)

Equipment enclosures are filled with pressurised gas that will prevent the entry of flammable gas, thereby preventing ignition. Although this equipment is not explosion-proof, it can be used in hazardous areas because internal components are not exposed to flammable gases. 

Dust protection (Ex t)

Equipment for areas where there are flammable dusts are classified as Ex tD and Ex t. Ex tD refers to enclosures whereas Ex t indicates overall protection against ignition from heat, sparks, or static electricity. 

Intrinsically safe two-way radios

Communication is always important in the workplace – doubly so when workplace hazards are present. In explosive atmospheres, you can have confidence in intrinsically safe, tested and certified two-way radios. At Radiocoms, we recommend the MOTOTRBO DP4401EX ATEX, MOTOTRBO DP4801 ATEX, and the MTP8000Ex Series TETRA ATEX portable radio.

Apart from being intrinsically safe, they support workplace safety with man-down and lone worker functions as well as a dedicated emergency button. Our industrial clients rely on Radiocoms to keep their workers connected, selecting durable devices to suit their workplace contexts. In hazardous areas, we rise to the challenge with MOTOTRBO. Consult us about your communication needs today. 

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