I had quite the concerning smell coming from my HVAC vents at the beginning of this past winter. I barely detect it at first. I had just started using my furnace as it was starting to get genuinely chilly in the last week of November. By the first week of December, the odor I was smelling was faint but unmistakable, at least, I thought it was. The odor coming from the heat exchanger vents was very much akin to gas. In my life, I have learned to not mess around with gas smells, so I actually ventilated my home and then vacated it immediately and called an HVAC technician. It turns out the odor wasn’t exactly what I thought it was. The HVAC technician asked me where the gas smell was coming from and I told him that it was clearly originating from the vents. He told me that it was almost entirely certain to be safe enough for him to come out and inspect the home, because he suspected that he knew what the problem was, and it wasn’t gas. When he arrived, his suspicions were confirmed. It turns out that dust can gradually accumulate on the heat exchanger throughout the year. I suppose that’s entirely to be expected, but once you first start using your heater in the winter, that heat can cause the dust to emit a burning smell. It turns out that this burning smell from the dust is very similar to the smell of gas. I was just relieved that it wasn’t a gas leak or something and I just needed to clean my heat exchangers!