Intrinsically safe design consulting
Hazardous Locations Design Consulting


There are obviously several ways to prevent an ignition from occuring. As a result, several different methods have been developed to ensure safety in hazardous locations. Each "protection technique" is codified in an equipment standard to help ensure that the required level of safety is always maintained. All equipment intended for use in potentially explosive atmospheres must use a recognized (published) protection technique.

Not all protection techniques are considered equally safe. Some are adequate for high-risk areas where an explosive atmosphere is always present, while some are only intended for lower-risk areas.

In the ATEX and IEC schemes, each protection method is designated by a letter "code", which specifies what technique was used during equipment design. While these codes are only used in ATEX and IEC, they are often generally used as a convenient way to identify hazardous locations equipment.

A sampling of the more common IEC lettering codes is shown below. Please click on a protection type for more detail as to how it works and where it is considered useful.

Letter Type of protection used

'd' Explosion-proof / flameproof enclosure
'e' Increased safety
'i' Intrinsically safe
'm' Encapsulation
'n' Non-incendive / non-sparking
'nR' Restricted breathing
'o' Oil immersion
'p' Pressurization
'q' Powder filling
't' Protection by enclosure
'h' Non-electrical equipment

Go to Certification Standards.
Go to Understanding ATEX.
Go to Understanding IEC 60079.

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