The setup
- House
- Hypothetical 1940s brick home with a full basement and an older forced-air furnace
- Season
- February, during the late-winter breeding season
- Where it happened
- Side yard, beside a basement window near the furnace room
- First sign
- Strong smell throughout the house within minutes of the heat cycling on
The situation
Illustrative example. Not a real job or customer.
On a cold February night, a hypothetical household wakes to a strong sulfur smell everywhere in the house. They are not sure whether it is gas or skunk. The smell seems strongest in the basement near the furnace.
- Unsure of the source, the household leaves the house and calls the gas utility from outside.
- A utility technician checks the appliances and lines and finds no leak; the technician notes the skunk-like smell is strongest near a basement window.
- Back inside, the household switches the furnace fan to auto and closes the furnace room door.
- In daylight, they find disturbed snow and soil at the side of the house below the window and a strong smell on the window frame.
- An HVAC technician finds unsealed return duct joints in the basement close to that wall, and the filter smells strongly.
- The exterior spray zone is treated, the window frame and sill are cleaned, and the gap around the old window is sealed.
- The return joints near the wall are sealed, the filter is replaced, and the ductwork is cleaned and treated; a whole-house treatment follows.
With the source treated and the return leaks sealed, the house stops smelling when the furnace runs. No den was found on the property, so the skunk was likely passing through during the roaming season. The household keeps the gap at the window sealed and checks the side yard after mild spells.
Keeping warm while dealing with it
Winter adds a constraint: the furnace cannot simply be shut off for days.
Run the fan on auto only
Heating still runs, but the blower is not moving air continuously between cycles.
Lower the setpoint slightly
Fewer and shorter cycles mean less air drawn past the leak until it is sealed.
Use space heaters with care
If a room is kept warm with a portable heater, keep it clear of fabric and furniture, and never leave it running unattended.
Air out at the warmest part of the day
Opening windows on the far side of the house for short periods at midday helps without chilling the house overnight.
Do not seal and run ozone in an occupied house
Air treatments that require an empty home are much harder to schedule in winter; plan any such step for a day the household can be away.
Common questions
Was calling the gas utility an overreaction?
No. Skunk odor and the gas odorant are closely related, and the smell was strongest near the furnace. Ruling out gas first was the correct order.
General information for Washington Park, not a quote or professional advice. In an emergency, call 911.