Why does my vacuum cleaner smell damp after I cleaned the filter?

A damp smell usually means the filter, dust container or brush head was refitted before it had fully dried. Do not use the vacuum cleaner until every washed part is completely dry, because the manuals warn against using a wet or damp filter.

1. Switch off and unplug the appliance, then remove the filter and dust container again. Check whether either part still feels cool, moist or heavy. Expected result: the smell should make sense as trapped moisture if the parts are not fully dry.
2. Leave the washed parts in a clean, dry place until they are completely dry to the touch. Do not use a hair dryer unless the manual for your model specifically allows it, as some manuals explicitly say not to do this. Expected result: the smell should lessen after full drying.
3. Reassemble the filter and dust container carefully, making sure each part locks into place. Expected result: the vacuum should start and sound normal again when dry parts are refitted correctly.
4. If the smell becomes musty, electrical or burnt, stop using the appliance immediately. Expected result: none, this is a stop-use point.
5. If the smell returns after proper drying, contact the retailer or store where the vacuum cleaner was purchased.