▁with ▁the ▁C lean ▁Air ▁Act ▁in ▁" sm oke ▁control ▁areas ", ▁an ▁ex empt ▁app liance ▁or ▁fuel ▁must ▁be ▁used . ▁ ▁US ▁poll ution ▁control ▁requirements ▁The ▁United ▁States ▁C lean ▁Air ▁Act ▁requires ▁that ▁wood ▁st ov es ▁be ▁cert ified ▁by ▁the ▁Environment al ▁Prote ction ▁Agency ▁( E PA ). ▁ ▁However , ▁the ▁E PA ▁had ▁no ▁mand atory ▁emission ▁limits ▁for ▁pel let ▁st ov es , ▁ind oor ▁or ▁out door ▁wood ▁bo ilers , ▁m ason ry ▁st ov es ▁and ▁certain ▁types ▁of ▁wood ▁st ov es ▁that ▁are ▁ex empt ▁from ▁E PA ▁reg ulation . ▁E PA ▁developed ▁new ▁reg ulations ▁which ▁began ▁to ▁come ▁into ▁effect ▁in ▁ 2 0 1 5 , ▁establish ing ▁mand atory ▁emission ▁limits ▁for ▁almost ▁all ▁wood - burn ing ▁app li ances ▁( fire p laces , ▁chim ene as , ▁and ▁some ▁other ▁special ▁app li ances ▁will ▁still ▁be ▁ex empt ). ▁ ▁In ▁ 2 0 1 9 , ▁E PA ' s ▁mand atory ▁smoke ▁emission ▁limit ▁for ▁wood ▁st ov es ▁in ▁ 2 0 1 9 ▁was ▁ 4 . 5 ▁gr ams ▁of ▁smoke ▁per ▁hour ▁( g / h ) ▁under ▁Step ▁ 1 ▁of ▁the ▁re vised ▁standards ▁of ▁performance ▁for ▁wood ▁burning ▁room ▁he aters . ▁Washington ▁State ▁has ▁also ▁had ▁requirements ▁of ▁a ▁maximum ▁of ▁ 4 . 5   gram s ▁per ▁hour . ▁▁ ▁On ▁May ▁ 1