In　this　paper,　the　effect　of　hydrogen　(H-2)　addition　on　the　pollutant　emissions　of　an　IDF　(inverse　diffusion　flame)　burning　LPG　(liquefied　petroleum　gas)　has　been　studied.　Pollutant　emission　behavior　was　intensively　investigated　at　fuel　lean　condition,　and　CO2,　CO,　HC,　and　NOx　emitted　from　the　flame　were　measured　with　their　emission　indices　reported.　HC　and　CO　emissions　are　highly　dependent　on　overall　equivalence　ratio,　and　both　HC　and　CO　are　very　high　at　fuel　lean　condition　while　reduce　to　nearly　zero　at　equivalence　ratio　larger　than　0.8　in　LPG-H-2　IDF.　NOx　emission　follows　the　trend　of　HC　due　to　N2O-intermediate　and　Fenimore　mechanisms　at　fuel　lean　condition　while　NOx　emission　increases　with　equivalence　ratio　at　fuel　rich　condition　due　to　thermal　NOx　mechanism.　Hydrogen　addition　is　found　to　promote　the　conversion　of　CO　and　HC　into　CO2,　and　there　exists　a　threshold　fraction　of　hydrogen　over　which　a　significant　reduction　of　CO　and　HC　occurs.　High　air　jet　Reynolds　number　tends　to　induce　poor　combustion　and　thus　increasing　HC,　CO　and　NOx　emissions.　Compared　to　LPG　IDF,　LPG-H-2　IDF　starts　to　generate　noticeably　CO　and　HC　emissions　earlier,　and　both　CO　and　HC　emissions　are　heavier.　(C)　2016　Elsevier　Ltd.　All　rights　reserved.