Hazardous Areas Explained

European Conformity Mark

EN Certifying Body ID Code

Mark for Explosion Protection

Means that apparatus is design Tested in accordance with ATEX Directive 94/9/EC.

Equipment Group

• Group I – firedamp (mining only)
• Group II – Surface industry only

Equipment Category

ATEX does not allow for the possibility of zone variances in apparatus. The category system means that the manufacturer must demonstrate the ATEX H&S essential requirements by testing.

• Cat 1: zone 0, 20 = 1G or 1D : very high safety protection by 2 protective measures/ faults
• Cat 2: zone 1, 21 = 2G or 2D: sufficient safety by 1 protective measure/ fault
• Cat 3: zone 2, 22 = or 3G or 3D: sufficient safety during normal operation- manufacturers declaration

Explosion Proof

Type of Protection

For Zone 2 applications there are some alternatives

• Ex nA – non-sparking
• Ex nR – restricted breathing
• Ex nL – energy limited
• Ex nC – encapsulated, enclosed break, hermetically sealed, non-incendive sealed device

Gas / Equipment Sub Group

Gases are subdivided according to their MESG or the Maximum Experimental Safe Gap (derived from flameproof tests)

• Group IIA – MESG > 0.9 mm
• Group IIB – 0.5 mm ≤ MESG ≤ 0.9 mm
• Group IIC – MESG < 0.5 mm
• Group IIIC- Dust protected

Temperature Classes

• Referred to as the “T” rating
• The T Class of equipment relates to the maximum surface temperature of the equipment and the Auto Ignition Temperature or AIT of the hazardous material
• A high AIT does not make the hazardous material less dangerous. It can actually make them more dangerous as they will burn much hotter

• T1 – ignition temp. > 450°C
• T2 – ignition temp. > 300°C
• T3 – ignition temp. > 200°C
• T4 – ignition temp. > 135°C
• T5 – ignition temp. > 100°C
• T6 – ignition temp. > 85°C

• T6 rating is appropriate for ALL hazardous areas
• As T-max does not exceed 85°C so it will not ignite ANY hazardous material

NB. Group II apparatus is divided into T classes according to its maximum surface temperature. In the same manner, gases are classified on the basis of different ignition energies of the different gases but still using these T - ratings

Equipment Protection Levels (EPL)

IEC 60079 standards now include provision for equipment on the basis of risk. If the consequences of an explosion are deemed particularly severe, then to decrease the risk, the category/zone relationship can be changed to give a lower possibility of ignition. So category 2 apparatus could be selected for use in a zone 2 for instance

Ambient Temperature

• The T class indicates the maximum temperature of surfaces which could ignite an external explosive atmosphere
• Unless indicated, the ambient temperature range for which the equipment is intended is -20C to + 40C
• If the T amb range is other than standard, the T-Class will be followed by the applicable ambient for example:
  T4 (65C Amb)
  (would mean that the equipment would not exceed its T4 rating (135C) EVEN IF the ambient temperature gets as hot as 65C)

Dust Protection

Dust is every bit as dangerous as gas and as such it has now become essential to hazardous area certification. Every enclosure now must be tested in a dust chamber and at indEx we have the most up to date certification tests.

Basically the same principles apply as with the gas label.

However there are differences:

• II 2 D = Surface industry, equipment category, dust
• tb = Protection by enclosure (IEC 60079-31)
  ta = Zone 20
  tb = Zone 21
  tc = Zone 22
• IIIC = Equipment Sub Group (Dust)
• T85°C = Maximum surface temperature of enclosure
• Db = Equipment protection level – this is a zone 1 for instance
• IP66 = Ingress protection – IP6X means complete protection from dust