Ferrous cable trays expand with the increasing heat from accidental fire. This has been proven by the German Otto-Graf-Institut Test Report III.1-80999/Tei/tei "Supplementary Test On The Topic Of Mechanical Force Acting On Cable Penetration Firestop Systems During The Fire Test", dated 23 October 1984, to dislodge "soft" firestops, such as those made of fibrous insulations with rubber coatings. This also applies to any silicone foam seals, but is easily remedied through the use of firestop mortars of sufficient compression strength and thickness, as shown above. Also, some building codes mandate that penetrants such as cable trays are installed in such ways so as to avoid their contribution to the collapse of a firewall.