With Um and Ui applied, the intrinsically safe circuits in electrical apparatus of level of
protection "ic" shall not be capable of causing ignition in normal operation and under the
conditions specified in this standard.
In testing or assessing the circuits for spark ignition, a safety factor of 1,0 shall be applied in
accordance with 10.1.4.2. The safety factor applied to the voltage or current for the
determination of surface temperature classification shall be 1,0.
NOTE The concept of countable faults does not apply to this level of protection. Infallible components and
assemblies, as in Clause 8, are not applicable. For level of protection “ic”, the term ‘infallible’ should be read as
‘meeting the requirements of 7.1’.