Four tests per fan
Draw test
Turn the fan on and hold one square of tissue just below the grille. It should be pulled firmly against the grille. If it flutters or falls, airflow is weak.
Exterior flap test
With the fan running, find the matching roof jack or wall cap outside. The damper should open. Binoculars help with roof vents.
Duct path check
From the attic hatch, follow the duct with a flashlight. Note any disconnection, crushing, long sags, or an end lying in the insulation.
Clear-time test
After a hot shower, time how long the mirror takes to clear with the fan running. Slow clearing points to a weak fan or blocked duct.
Results log
| Bathroom | Tissue test | Exterior flap opens | Duct condition | Mirror clear time | Action needed |
|---|---|---|---|---|---|
| Primary bath | Pass / weak / fail | Yes / no / not found | Connected / loose / unknown | Minutes | Notes |
| Hall bath | Pass / weak / fail | Yes / no / not found | Connected / loose / unknown | Minutes | Notes |
| Basement bath | Pass / weak / fail | Yes / no / not found | Connected / loose / unknown | Minutes | Notes |
| Powder room | Pass / weak / fail | Yes / no / not found | Connected / loose / unknown | Minutes | Notes |
| Laundry | Pass / weak / fail | Yes / no / not found | Connected / loose / unknown | Minutes | Notes |
What your results mean
- IfWeak tissue test, duct connected, flap opensThenClean the fan grille and blades. If still weak, the motor may be failing or undersized.
- IfGood draw inside but no flap opens outsideThenThe duct may be disconnected or ending in the attic. Check from the hatch.
- IfDuct end lying loose in insulationThenHave it reconnected to a proper exterior termination and inspect the sheathing above for staining.
- IfBasement bath fan with no visible exterior ventThenAsk a contractor to trace where it goes; basement fans sometimes run long distances or into joist bays.
- IfAll tests pass but mirror clears slowlyThenRun the fan longer, consider a timer switch, and leave the door open after showers.
Common questions
How often should I repeat these tests?
Once a year is a good habit, ideally in late fall before the cold months when a failed duct does the most harm. Repeat the duct check any time someone has worked in the attic, such as an insulation, cable or solar installer.
My fan is very quiet. Is that a problem?
Not necessarily. Many newer fans are designed to run quietly. The tissue test and the exterior flap test tell you more about performance than the sound does.
Should the fan run during the whole shower?
Yes. Turn it on before the water and leave it running for a while afterward, until the mirror and walls are clear.
General information for Highlands Ranch, not a quote or professional advice. In an emergency, call 911.