▁force ▁of ▁a ▁ 3 0 ▁p si ▁water ▁stream . ▁The ▁pill ows ▁are ▁com pressed ▁to ▁provide ▁sufficient ▁strength ▁to ▁with stand ▁the ▁h ose ▁stream ▁impact ▁of ▁the ▁test . ▁To ▁accommod ate ▁larger ▁open ings ▁that ▁can ▁allow ▁the ▁pill ows ▁to ▁become ▁dis l od ged , ▁wire ▁mesh ▁is ▁sometimes ▁used . ▁As ▁a ▁particular ▁compression ▁rate ▁is ▁required ▁for ▁each ▁hole , ▁the ▁area ▁of ▁the ▁opening ▁less ▁the ▁area ▁covered ▁by ▁the ▁pen etr ating ▁items ▁is ▁calculated , ▁resulting ▁in ▁the ▁number ▁and ▁size ▁of ▁the ▁pill ows ▁to ▁be ▁installed . ▁Without ▁this ▁information , ▁there ▁is ▁no ▁evidence ▁the ▁installation ▁con forms ▁with ▁the ▁requirements ▁of ▁the ▁cert ification ▁listing . ▁As ▁pen etr ants ▁are ▁ex changed ▁or ▁removed , ▁this ▁calculation ▁is ▁red one ▁to ▁maintain ▁comp liance ▁with ▁the ▁cert ification ▁listing . ▁ ▁An ▁installation ▁that ▁meets ▁listing ▁and ▁appro val ▁use ▁and ▁comp liance ▁usually ▁requires ▁pill ow ▁coverage ▁between ▁c ables . ▁The ▁type ▁and ▁size ▁of ▁the ▁pill ows ▁used ▁must ▁be ▁matched ▁to ▁the ▁exact ▁cab ling ▁per ▁the ▁cert ification ▁listing . ▁Sm oke ▁will ▁migr ate ▁through ▁the ▁interior ▁of ▁a ▁cable ▁bundle ▁if ▁the ▁bundle ▁is ▁not ▁opened ▁up ▁and ▁se aled ▁on ▁the ▁inside ▁during ▁the ▁installation ▁of ▁any ▁fir est op , ▁regardless ▁of ▁whether ▁the ▁fir est op ▁is ▁int umes cent ▁or ▁not . ▁If ▁mesh ▁is ▁used , ▁mechanical ▁fast en ers ▁are ▁required , ▁potentially