Dreo points first to water quality, stale water, cleaning/drying, and the aroma-pad tray—not an internal repair.
Does this match what you are seeing?
Owners often describe this same Dreo HM713S symptom in different words. These phrases all stay on this one model-specific guide rather than creating duplicate fix pages.
- Dreo HM713S smells bad
- Dreo HM713S mist smells strange
- Dreo HM713S unpleasant odor from humidifier
- Dreo HM713S smells after cleaning
Check these in order
- Use purified or distilled water.
- Change the water regularly.
- Clean the humidifier, then let it dry for about 12 hours with the cover detached.
- Clean the aroma-pad tray and replace the aroma pad if needed.
Diagnostic decision path
Dreo treats unpleasant HM713S mist odor as a water-and-cleanliness problem first. The useful distinction is between stale/mineral-laden water or an aroma-pad source and a burning/electrical smell, which should end troubleshooting immediately.
- Identify whether the odor smells stale/musty or hot/electrical before continuing.
- Empty old water rather than topping it off with fresh water.
- Keep essential oil confined to the aroma-pad system, not the water tank.
If: Tap water or old standing water is producing the odor
What it means: Water quality or microbial buildup is a more likely source than an internal electrical fault.
Do next: Empty the unit, switch to purified or distilled water, and change the water regularly.
If: The tank/base smells even after fresh water is added
What it means: Residue in the wetted parts can continue to contaminate new water.
Do next: Clean the humidifier, then leave it dry for about 12 hours with the cover detached before refilling.
If: The odor follows use of the aroma feature
What it means: The aroma pad or tray can retain an old scent or residue.
Do next: Clean the aroma-pad tray and replace the pad before judging the water/mist path again.
If: The odor is burning, electrical, or accompanied by abnormal heat
What it means: This is outside Dreo’s normal “unpleasant mist smell” cleaning case.
Do next: Turn the HM713S off, unplug it, and stop use pending Dreo support.
How to interpret the retest
Use “Tap water or old standing water is producing the odor” to decide which documented branch to test next, not to declare the cause on its own. On the Dreo HM713S, it corresponds to “Water quality or microbial buildup is a more likely source than an internal electrical fault”. Use “Use purified or distilled water” and retest. When the observation is present, continue with “Empty the unit, switch to purified or distilled water, and change the water regularly”. When it is absent, rule out that explanation for now and keep the result with the current Dreo HM713S unpleasant smell notes.
Make this one change, then compare the result with the original state. Check “Change the water regularly” on the Dreo HM713S, then look specifically for “The tank/base smells even after fresh water is added”. A match supports the manual's interpretation “Residue in the wetted parts can continue to contaminate new water” and sends you to “Clean the humidifier, then leave it dry for about 12 hours with the cover detached before refilling”. If the observation is missing, that result narrows the Dreo HM713S unpleasant smell diagnosis without jumping to an unrelated reset.
This possibility becomes relevant when you can reproduce “The odor follows use of the aroma feature”. For the Dreo HM713S, use “Clean the humidifier, then let it dry for about 12 hours with the cover detached” as the controlled test. If the same observation appears, the source meaning is “The aroma pad or tray can retain an old scent or residue” and the next action is “Clean the aroma-pad tray and replace the pad before judging the water/mist path again”. If it does not appear, record the non-match and continue through the remaining Dreo HM713S checks for unpleasant smell.
Use this as the first controlled change: “Clean the aroma-pad tray and replace the aroma pad if needed”. After that change, compare the Dreo HM713S with “The odor is burning, electrical, or accompanied by abnormal heat”. A match supports the documented reading “This is outside Dreo’s normal “unpleasant mist smell” cleaning case” and then “Turn the HM713S off, unplug it, and stop use pending Dreo support”. If the comparison fails, step away from this Dreo HM713S path and continue; that non-match helps rule out this explanation for the unpleasant smell complaint.
Model-specific context that changes the diagnosis
Two Dreo HM713S clues that point to different fixes
Identify which of these two states matches the unit before trying another correction. If you can reproduce “Tap water or old standing water is producing the odor” on the Dreo HM713S, continue with “Empty the unit, switch to purified or distilled water, and change the water regularly” because the documented meaning is “Water quality or microbial buildup is a more likely source than an internal electrical fault”. If you reproduce “The tank/base smells even after fresh water is added” instead, use “Clean the humidifier, then leave it dry for about 12 hours with the cover detached before refilling” because that state is interpreted as “Residue in the wetted parts can continue to contaminate new water”. Test those two possibilities separately.
Run the Dreo HM713S checks in order
Keep the starting conditions steady so the result is easy to read. Try “Use purified or distilled water” on the Dreo HM713S and observe the same complaint. Only then move to “Change the water regularly” and, if necessary, “Clean the humidifier, then let it dry for about 12 hours with the cover detached”. With unpleasant smell on the Dreo HM713S, keeping the other obvious variables steady makes it easier to tell whether a documented condition was actually responsible.
Common mistakes that make this harder to diagnose
- Masking stale-water odor by adding more fragrance.
- Leaving old water in the reservoir between cleaning cycles.
- Putting essential oil directly into the water path.
- Continuing to run the humidifier when the smell is clearly electrical rather than musty.
The odor problem is resolved when clean purified/distilled water in a cleaned and fully dried HM713S produces neutral-smelling mist and the aroma tray is no longer carrying stale residue. Burning or electrical odor always remains a stop-use condition.
Questions people ask about this exact symptom
Why does my Dreo HM713S have an unusual odor?
For the Dreo HM713S, Dreo points first to water quality, stale water, cleaning/drying, and the aroma-pad tray—not an internal repair. For this unpleasant smell check on the Dreo HM713S, start with “Use purified or distilled water” and check the result before making another change. If the behavior is unchanged, continue with “Change the water regularly”.
What should I check first if my Dreo HM713S has an unusual odor?
Start with “Use purified or distilled water”. If the Dreo HM713S behaves the same, move to “Change the water regularly”; use “Clean the humidifier, then let it dry for about 12 hours with the cover detached” only after judging that result. For this unpleasant smell complaint, one change at a time gives you a cleaner before-and-after comparison than a batch of simultaneous fixes.
When should I contact Dreo about this Dreo HM713S problem?
Use Dreo support if the Dreo HM713S still has the same problem after the documented checks for unpleasant smell. Have the Dreo HM713S's last retest notes, current mode, and any warning light or code ready; tell support you followed the documented unpleasant smell checks. This safety boundary applies immediately at any point: “A burning or electrical smell is not this FAQ case—stop use and unplug the unit”.
Why this path is model-specific
These are the HM713S FAQ steps for unpleasant-smelling mist.
For the Dreo HM713S, the machine type matters: it is hybrid. Visible mist is part of normal output when mist production is active, so a true no-mist complaint deserves model-specific troubleshooting.
This symptom appears on other humidifiers too, but the meaning and reset path can change by technology, sensor logic, and control layout. Use the exact model source above before borrowing a fix from a neighboring model.
Compare this symptom across verified models
If you are still deciding whether this behavior is normal or model-specific, use the symptom hub to compare only manufacturer-linked guides. Keep the Dreo HM713S instructions above as the controlling path for this machine.
If the problem is still there
If the checks above do not change the symptom, use the manufacturer support path for this exact model. We intentionally stop before undocumented resets, sensor bypasses, internal mains work, or parts replacement that the consumer manual does not authorize.
What we do not recommend
Do not defeat a float, water-level sensor, overheat protection, interlock, or other safety feature. Do not open mains-powered sections for live testing. If the unit smells burned, becomes abnormally hot, sparks, leaks into electrical areas, or repeatedly trips a circuit, unplug it and use manufacturer service guidance.
Primary source for this diagnosis
Source checked during the September 4, 2026 editorial review. Manufacturer documents can change; a material re-review updates this guide’s reviewed date rather than stamping unrelated pages.