High Efficiency furnace?

our HE furnace has all kinds of safety shut-offs (for when the exhaust fan isn't working, condensate water building-up, overheating, etc., etc) just a guess would be that there is a clog in that exhaust pipe - not enough to shutdown the furnace, but restricting output (could be an animal got in there, water build-up, ice build-up). of course, what you normally see as exhaust is water vapor that looks "smoky" when it hits the outside air ---- conditions may be such that it isn't as visible as usual. service call to be safe.

That could be mercapton, a chemical added to natural gas to give it an odor that can be detected. I recommend that you immediately get out of the house, call a service man, notify the natural gas utility.

A Forced Air Gas Furnace is used in Central Home Heating System. It converts gas fuel in to usable amount of heat and circulate this heat in to entire house through conventional air ducts and vents. A high efficiency furnace is one of the most valuable ways of fulfilling home heating requirements, with its energy saving technology it offers saving huge amount of money on utility bills and provides dependable home heating comfort. Cambridge Heating and Home Services provide central heating and air conditioning services to the homeowners of Greater Toronto Areas.

one test you can do relatively safe is turn off gas to furnace. then set t-stat to call for heat. the inducer assembly will come on, listen to see if you hear water sloshing. if you do, you have a drain issue inside furnace. also, there is an inspection window in blower door panel. look through the window and see if you see a blinking of lights. those are fault codes and tell what your problem may be.