The gases which form an explosive atmosphere can be classified into 4 main groups, which are classified according to their two main characteristics:
IEMS: Interstitial characteristic of a given air/gas mixture, which extinguishes the flame of an explosion.
EMI: minimum energy that must be supplied to the explosive atmosphere to cause the explosion of the mixture. Depending on the group to which the ATEX equipment belongs, it will protect against one type of gas or another.
