This rule amends regulations promulgated under section 608 of the Clean Air Act to exempt certain hydrocarbon refrigerant substitutes from the existing prohibition on knowingly venting, releasing, or disposing of refrigerant substitutes by any person maintaining, servicing, repairing, or disposing of appliances or industrial process refrigeration. In a prior action, EPA recently listed these hydrocarbons as being acceptable subject to use conditions as substitutes for ozone depleting substances under EPA's Significant New Alternative Policy Program. This final rule is based on current evidence that venting, release or disposal of these hydrocarbon refrigerant substitutes do not pose a threat to the environment. Specifically, EPA is exempting from the venting prohibition isobutane (R-600a) and R-441A, as refrigerant substitutes in houshold refrigerators, freezers, and combination refrigerators and freezers, and propane (R-290), as a refrigerant substitute in retail food refrigerators and freezers (stand-alone units only).