ASTM E1725 Fire Resistive Barrier Test Question

[ben5446]

Why does ASTM E1725 consider a failure to occur when the average test temperatures exceed 139°C? It seems to me that the majority of low temperature cables have a maximum operating temperature of 90°C or 105°C?

 

[7anoter4]

The temperatures measured by the thermocouples attached to the conductor determine the fire-resistive performance of the enclosure surrounding the copper conductor. Ratings, such as 1-hour or 2-hour, are based upon the ability of the enclosure or barrier to limit the average temperature rise along the bare copper conductor to 250°F [121Co] and limit the temperature rise at any point on the conductor to 325°F [162Co]. Similar temperature limits are included in the test methods for building assemblies and barriers for cables.
The rated temperature of normal PVC is 70 Co .Special PVC may withstand 105 Co. XLPE or EPR withstand 90 Co for indefinite time.
For a short time PVC may withstand 150 and XLPE 250 Co.
Never the less, I think the purpose of the temperature limits in this standard are not in order to assure ability of the insulation to be ready to be returned into operation but to avoid to set fire to other insulating material as paper [or similar] or elastomers with low fire resistance [ in contact or in vicinity of these wire].
Regards