Use this page with your nose, a notepad and an open window. Walk through the RV in the cool of the morning with windows open and the equipment off, and write down where each smell is strongest. A smell that seems to be everywhere often has a single source that the air system is carrying around. Narrowing it by place, timing and quality gets you to a short list of causes without taking anything apart.
The finder below is a starting point, not a diagnosis. Safety smells, especially gas, come first and are covered on their own page. For everything else, the aim is to match smell quality to the right suspect, then confirm by checking that location.
Start with the quality of the smell
- IfSulfur or rotten egg near the toilet or sinkThenCheck the drain trap, the gray tank vent and the black tank seals. See the tank guides.
- IfGas-like smell near the stove or furnaceThenTreat as a safety issue and follow the propane guide before anything else.
- IfMusty, earthy smell near walls, windows or roof ventsThenSuspect water intrusion and check seals, stains and soft spots.
- IfSweet, heavy smell from one spotThenLook for a dead animal in a void, behind the refrigerator or in the floor.
- IfSharp ammonia-like or stale animal smellThenLook for nesting material, droppings and entry points.
- IfBurnt toast or dust smell on first heatingThenLikely dust burn-off in the furnace, but see the first-run guide.
- IfSmoke or ashtray smell on warm daysThenCheck fabric, headliner, filters and the duct system.
- IfFuel or exhaust smell while drivingThenPull over safely and have the vehicle checked.
Timing clues
| When it appears | What it suggests | Where to look |
|---|---|---|
| After showering | Humidity or drain issue | Bathroom vent, shower pan, gray tank |
| On warm afternoons | Heat-released material or organic residue | Cab, mattress, trash, fridge |
| When the fan runs | Air system source | Filter, ducts, intake |
| After rain | Leak | Roof, slides, windows, vents |
| After travel | Loosened seal or tank | Roof vent, valves, hoses |
| Only when parked in storage | Mold or animals | Cabinets, bed base, wall voids |
Notes to write down as you go
- The room or cabinet where the smell is strongest
- The temperature outside and inside
- Whether the smell changes with the fan, shower or sun
- Any stains, soft spots, droppings or moisture
- What you changed since last time, such as a new cover or cleaner
- Photos of anything unusual
If you still cannot tell
Clean one suspect at a time
Change one thing, then wait a day before changing another.
Seal off a section
Close doors and cabinets, wait, and smell again.
Use a simple moisture meter
Check walls and floors near suspects for dampness.
Ask for a second nose
A friend or technician may notice what you no longer smell.
Common questions
Why do I stop smelling it after a few minutes?
Noses adapt to steady odors. Step outside for a minute and re-enter for a fresh reading.
Can two sources be involved?
Yes. A damp bathroom and a drain can overlap, so fix the most likely first and reassess.
General information for the Denver area, not a quote or professional advice. In an emergency, call 911.