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Fire & Explosion Safety
Electrical Equipment
Duct Penetration
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Explosive Atmosphere
Explosion Hazard
– A mixture of air, under atmospheric conditions,
and flammable gas, or vapour
– Capable of self-sustaining propagation upon
ignition
– Hazardous. If exploded, can cause damage
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Conditions for Explosion Hazard
AIR
Event of simultaneous occurrence of
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Explosion Protection Concept
Explosion protection by removing one of the threefactors in fire triangle
1. Primary Protection (make safe)• Prevention of explosive atmosphere, example
– Ventilation
– inertization
2. Secondary Protection (encompass all electrical
apparatus used in hazardous areas)• Prevention of the ignition of explosive atmosphere
• Comply with IEC/EN 60079 or AS60079
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Hazardous Area Classification
• Explosive atmosphere is present, or may be
present for long period
• Allows selection of appropriate certifiedequipment
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Hazard Probability
• Zone 0
• Explosive gas atmosphere is present continuously
• Zone 1
•Explosive gas atmosphere is likely to occur in normaloperation
• Zone 2
• Explosive atmosphere is not like to occur in normal operation
• Non hazardous
• Explosive gas atmosphere is never present
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Gas or Apparatus Group
Decreasing MIE
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Ignition Characteristics
GAS OR
VAPOUR
LEL % UEL % MIE (µJ)
Propane 1.7 10.9 180
Ethylene 2.3 36 60
Hydrogen 4.0 77 19
Source: EEHA note
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LEL & UEL
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Explosive Limits (LEL & UEL)
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Temperature Class
Hydrogen auto ignition temperature is 560 C. Resultant classification may be T1.
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Typical Details
Duct Penetration B Wall
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Fire Damper
• Automatic closure of damper blade activated
by temperature (68-79C) within the duct
– Rupture of frangible bulb causes the spring return
or operation of pneumatic actuator
• Manual closure independent and can override
the automatic means of control
– Operation may be pneumatic or electric
• Open/close Indication of damper
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