When building install an energy efficient heat pump. If you own and your unit is older than ten years, it may make sense to install a new energy efficient heat pump.
Heat pumps are safe because they are flameless and flueless.
Keep your air conditioning thermostat at 78 degrees during the summer and your heating at 68 degrees during the winter. Properly installed ductwork is necessary for operating efficiency for all types of heating and cooling systems. Inspect the ductwork for loose duct joints or sagging duct runs. Ductwork should be securely taped or sealed at all seams and joints. Cover with either rigid board or blanket type insulation.