If you are planning explosion protection for a particular hazardous area, it’s important to know what combination of Zone 0, Zone 1 and Zone 2 equipment you will need.
The difference between the three can be approximated as follows:
- Zone 0 equipment should be used where there is a continual presence of highly flammable or explosive chemicals.
- Zone 1 equipment should be used where there is likely to be a frequent presence of flammable or explosive substances.
- Zone 2 equipment should be used where inflammable or explosive vapours are likely to accumulate occasionally, but not often.
Writing in July 2015’s Chemical Engineering, Robert Schosker went into more detail about the zones and how they relate to real-world hazardous areas.
For instance, he gave the example of a gasoline storage tank without a floating roof, but with a roof vent and a circular dike surrounding it.
The area within five feet of the roof vent is classified as a Class I, Division 1 hazardous area; from five feet to ten feet it becomes a Class I, Division 2 hazardous area.
Zone 0 is the area inside the tank itself; Zone 1 is the area immediately around the vent; and Zone 2 equipment should be used anywhere within about ten feet of the tank and inside the surrounding dike.
Although this is a specific example, the general applications are as described in the bullet points above – and it’s often best to err on the side of caution, as Zone 0 equipment can be used in Zone 1, and so on.