Post <a href="//commons.wikimedia.org/wiki/Fire_test" title="Fire test">fire test</a> pictures showing how 3/4 in. thick acrylonitrile butadiene/polyvinyl chloride (AB/PVC) flexible foam pipe covering can go through the seal unhindered. It was wrapped inside the mortar with an intumescent wrap strip, which stopped the fire. There was no autoignition of the insulation due to flame retardants inherent in its organic composition. This version of the mortar preceded the switch to gypsum.
<a href="//commons.wikimedia.org/wiki/User:Achim_Hering" title="User:Achim Hering">Achim Hering</a>
2007-06-25
<span class="int-own-work" lang="en">Own work</span>