Michael Hart, San Diego duguden dɔ, jalaki don a ka sariya tiɲɛni la, min ɲɛsinnen bɛ ka dɔ bɔ gazi minnu bɛ na ni fiɲɛ ye. A ma bɛn ni sariya ye ka idɔrɔfluoro karbɔniw (HFC) ladon ka sɔrɔ ka u sɔrɔ ka ɲɛsin u ma, min ye Environmental Protection Agency (EPA) ka sira ye.