On days when there is high humidity in the air, and you walk past the furnace you can small a slight gas odor because the natural rising air currents that would carry that slight odor up and away from your nose, are reversing, and the gas vapors are clinging to the moist heavy air molecules, before they can evaporate, your sensitive nose catches them. On dry days you probably don't notice the smell. Natural gas is odorless, and the gas company goes to great expense to add an odor, for that very reason, to allow you to detect a leak and take necessary precautions. Please be very careful. If its more than just a slight oror, and if you also smell it on dry warm days, call the gas comapny and ask them to bring a sniffer with them. They have an electronic air quality sensor that is much more sensitive than your nose and they'll tell you if there's any cause for concern.
: Sometimes I can smell a slight natural gas smell around my furnace. At other times I can't smell anything. I have sprayed soapy water on the pipe conections and don't see any signs of a leak. The furnace is 5 years old. Any ideas?