: I have septic odors coming from my roof vent, but only notice them during cold weather. Have seen mention of a filter that can be atached to the vent. Do they work? And, where can they be found?Check the height of the vent. Is it too low to the roof, is it near a window etc. In cold weather the odours will hang around longer. Have you put too much household disinfectant or cleaners into the tank and killed off the bacteria. A properly working septic tank does not give off much odour.