| potential ignition source that is able to ignite an explosive atmosphere when consideration is taken of when it occurs (i.e. in normal operation, expected malfunction or rare malfunction)|
Note 1 to entry: This is important for establishing the EPL.
Note 2 to entry: An effective ignition source is a potential ignition source which can ignite the explosive atmosphere if protective measures are not used.
Note 3 to entry: For example, the frictional heat that can be produced by a bearing is a possible ignition source. This is an equipment-related ignition source if the piece of equipment contains a bearing. If the energy that can be produced by the friction in the bearing is capable of igniting an explosive atmosphere, then this is a potential ignition source. Whether this potential ignition source is effective depends on the likelihood that it will occur in a particular situation.