It may be time to buy a new furnace. Experts say failing to know just when that time comes could mean you’re in the cold this winter, or in danger of poisoning or death from carbon monoxide. Retired ISU extension ag engineer Tom Greiner says a heating professional should look over your system yearly, and can give you qualified advice. Greiner says the ones he’s met aren’t trying to push people into buying new furnaces or water heaters. Greiner says many try to help keep old furnaces operating a little longer because they feel customers can’t afford a new one. Greiner says far from saving money, trying to hang onto an old appliance for another few years could be an unwise energy decision.Greiner says new appliances are better, and more efficient — and a new furnace or water heater can typically save you 20- to 30-percent on your utility bills. Greiner says carbon monoxide causes more poisoning cases in the U.S. than all other poisons combined, so having a furnace in good working order is an important move for both economy and safety.