Michael Hart, ma odak San Diego, ne odonjne ni oketho chike mag sirkal mar Amerka ma ne dwaro geng'o tiyo gi gik ma kelo ler e ot. En gima ok owinjore gi chik mondo ng'ato oter hydrofluorocarbons (HFCs) e pinywa ka onge barua makende ma sirkal mar Environmental Protection Agency (EPA) ne ochiwo.