The difference between a product being ‘explosion proof’ and ‘intrinsically safe’ can be confusing but it is vital to select the proper one for your application.
Both approvals are meant to prevent a potential electrical equipment malfunction from initiating an explosion or ignition through gases that may be present in the surrounding area. This is accomplished in both cases by keeping the potential energy level below what is necessary to start ignition process in an open atmosphere.
What does this mean?
The term “intrinsically safe” describes a protection technique that limits the electrical and/or thermal energy of electrical equipment used in potentially explosive areas such that there is insufficient energy to ignite the hazardous gases or dust.
‘Explosion proof’ applies to an encased apparatus that is capable of withstanding a material explosion. Which means, if combustible gases entered the explosion proof housing and were ignited by the electrical energy within the housing, the resultant “explosion” would be contained inside the housing. The energy from the explosion would then be dissipated through the large surface of flanges or threads paths of the enclosure. By the time the “explosion” exits the housing, there is insufficient energy remaining to ignite the surrounding atmosphere.
How do I know which to choose?
Zone classification is one method for defining the level of risk in a hazardous area and determining which level of protection is required.
Zone 0: Area with permanent risk of explosive atmosphere of air and gas
Zone 1: Area with occasional risk of explosive atmospheres
Zone 2: Area of rare risk of explosive atmospheres of air and gas, only for short periods
Zone 20: Like Zone 0 except atmosphere of air and dust
Zone 21: Like Zone 1 except atmosphere of air and dust
Zone 22: Like Zone 2 except atmosphere of air and dust
Additional certifications and classifications used to determine both explosion proof and intrinsically safe approvals, including more in-depth divisions that explore application and environment specifics, can be found here.