Understand the basics of Ex Repairs

There are major differences between “d” and the capital “D” when looking at the labels of ATEX equipment – What is the difference?


There is a critical difference between the lower case letter d, as in Ex d, or Ex de, and the capital D, as in Ex tD or GD. They have two very different meanings, and knowing which one is which will determine the way the equipment is repaired and what standards are required.


Ex d

The lower-case “d” after an “Ex” indicates a flameproof machine. The equipment is designed specifically to operate where volatile gases and vapours could be present. This protection concept relies upon:

The enclosure containing an explosion should the surrounding gas enter the enclosure and become ignited, andEnsuring that the exhaust gases are sufficiently cooled before entering the surrounding atmosphere through flamepaths to prevent further ignition.


Ex tD, Ex pD, GD or Group III equipment:

The capital “D” stands for “Dust”, where the protection concept Ex tD uses high Ingress Protection (IP) enclosures (as per the table below) and controlled surface temperatures as the means of protection.