This part of IEC 61300 details a procedure to determine the suitability of a fibre optic device or closure to withstand the environmental condition of extended high temperature that may occur during operation, storage and/or transport. The test is intended to indicate the performance of such devices when exposed to heat of constant temperature over a given period.

In general terms, this test provides a high temperature to induce potential failures due to softening and expansions.

This procedure does not assess the ability of a device to operate during temperature variations; in this case, IEC 61300‑2‑22 would be used.