▁can ▁be ▁found ▁in ▁Building ▁Reg ulations ▁Appro ved ▁Document ▁J , ▁Section ▁ 2 , ▁Table ▁ 1 ▁" A ir ▁Supp ly ▁to ▁solid ▁fuel ▁app li ances ". ▁ ▁The ▁safe ▁operation ▁of ▁a ▁wood - burn ing ▁st ove ▁requires ▁regular ▁maintenance ▁such ▁as ▁empty ing ▁ash ▁p ans ▁( cont ain ers ) ▁beneath ▁the ▁wood ▁gr ate . ▁Rout ine ▁clean ing ▁of ▁the ▁st ove ▁pip es ▁and ▁chim ney ▁is ▁also ▁needed ▁to ▁prevent ▁chim ney ▁fires . ▁Cre os ote ▁and ▁so ot ▁gradually ▁build ▁up ▁in ▁st ove pip es ▁and ▁chim ne ys . ▁This ▁could ▁damage ▁the ▁chim ney ▁and ▁spread ▁fire ▁to ▁the ▁surrounding ▁structure , ▁especially ▁the ▁roof . ▁When ▁so ot ▁blocks ▁the ▁air flow ▁through ▁the ▁st ove ▁pip es ▁or ▁chim ney , ▁smoke ▁can ▁build ▁up ▁in ▁the ▁st ove ▁pip es ▁and ▁in ▁the ▁house . ▁ ▁The ▁basic ▁principle ▁of ▁cont rolling ▁comb ust ion ▁by ▁reducing ▁the ▁air ▁supply ▁means ▁that ▁very ▁often ▁there ▁is ▁a ▁reduction ▁zone / cond itions ▁within ▁the ▁st ove . ▁This ▁means ▁that ▁carbon ▁dio x ide ▁is ▁often ▁" redu ced " ▁to ▁carbon ▁mon ox ide , ▁which ▁is ▁highly ▁poison ous ▁and ▁must ▁not ▁be ▁allowed ▁to ▁escape ▁into ▁the ▁home . ▁This ▁can ▁occur ▁if ▁the ▁st ove ▁or ▁chim ney ▁has ▁not ▁been ▁clean ed ▁or ▁there ▁is ▁ins u fficient ▁vent ilation . ▁Car bon ▁mon ox ide ▁detect ors