Fundamentals of Zone 0

Hazardous locations are defined as those where fire or explosion hazards may exist due to the presence of flammable gases, vapours or liquids, combustible dusts, or ignitable fibres or flyings. 

Electrical equipment is often installed in locations where there are gases present,  making them hazardous locations. Therefore, it is required that these products to be designed and constructed as compliance with safety standards in order to be safe in use in such hazardous locations.

As per IEC standards, the classified areas are categorized in three groups: Zone 0, Zone 1 and Zone 2.

To make this even easier to understand, look at this diagram of a typical petrol station. The areas classified as Zone 0, Zone 1 and Zone 2 have been identified. In this animation, our focus is on the Zone 0 classified area.

Zone 0 is s an area where an explosive gas-air mixture is continuously present or present for long time. Therefore, devices that can pose an ignition must be safe under fault or even normal conditions.

In this illustration, we have a tank that contains flammable liquid. Above the flammable liquid inside the tank and given an ambient temperature above the flash point of the liquid, gas vapours can be present. This area is considered Zone 0 because the hazard exists continuously.

The product being used in this area must be safe. In order to be certified as compliant with safety Standards for Zone 0, the product must be protected by one or more of the following protection techniques: intrinsic safety with level of protection “ia”, encapsulation with “ma” protection and flameproof with “da” protection. Note that this flameproof protection applies only to portable combustible gas detectors with catalytic sensor.

Additionally, equipment containing optical radiation such as lasers can be installed in Zone 0 if optical power is inherently safe using “op is” protection or using an interlock system complying with “op sh” protection for Zone 0.