Intumsecent putty is ideal for sealing pipes, cables and service penetrations, especially ones with odd shapes. Red in colour, each 1kg tub of intumescent putty can give up to 4 hours of fire resistance - depending on how deep the coverage - and has been tested to BS476: Part 20:. Whether you need. The following charts give the number of 3M pillows needed to completely firestop an opening that cable tray passes through. Where cables pass through shafts, walls, slabs, or enter electrical panels or cabinets, openings shall be tightly sealed. Envirograf ® products are tested to British Standards & European Standards at approved test centres.