Why does my vacuum cleaner smell when I use it?

A vacuum has only a few things in it capable of producing a smell, and each one produces a distinctive one. The machine pulls all the air it moves past its own motor, so it is very good at broadcasting whatever it holds around the room. That is also why the smell is a useful diagnostic: it tells you which part of the airflow path has a problem before you have opened anything.

Safety

What you'll need

• Scissors or a seam ripper
• Cold water
• Replacement filters for the model (optional)
• A torch (optional)

Step by step

1. Unplug it and describe the smell before doing anything else.Hot and dusty, burning rubber, acrid electrical, musty and damp, or animal. They point at different parts of the machine and the fixes have nothing in common.
2. Acrid, sharp, plastic or electrical: stop here.Unplug it and leave it unplugged. That smell is insulation or windings, not dust. Check the plug and flex for heat or scorching, and if there is any, treat that as an electrical fault. This machine goes to a repairer or to WEEE recycling, not back into use.
3. Hot and dusty: treat it as restricted airflow.The motor is cooled by the air passing through the machine. Restrict the air and the motor runs hot, which bakes the dust already in the machine and produces the smell. Work through the path: bin or bag, pre-motor filter, hose, wand, floor head.
4. Drop a coin through the hose to prove it is clear.Detach the hose and hold it vertically. A coin should fall straight through. If it stops, something is lodged — a sock, a hair clip, a compacted plug of dust at a bend. Push it through with a broom handle rather than pulling from one end.
5. Burning rubber: look at the brush bar and its belt.Hair, thread and carpet fibre wrapped tight at the bar's ends stops it turning, and the belt then slips against a stationary bar and burns. Release the bar, cut the wrap off with a seam ripper, clear the bearing ends, and inspect the belt for glazing, cracks or a flat spot. A glazed belt is replaced, not refitted.
6. Musty or damp: find what went in wet.A filter refitted before it was fully dry, damp mud from the hall, a spill picked up with the vacuum, or a machine stored in a garage over winter. Wash the bin in warm soapy water, dry it completely, and wash or replace every filter — foam that has gone mouldy is replaced, not rinsed.
7. Animal or stale-sweet: replace the filters rather than washing them.Dander and skin oils saturate filter media and do not rinse out. A pet household usually needs the exhaust filter replaced every six months rather than annually. Wipe the inside of the bin and the hose interior too — a bottle brush and warm soapy water, dried thoroughly.
8. Clean the parts the airflow touches, not just the bin.Cyclone cones, the underside of the lid, the seal gasket, the inside of the wand and the floor head channel. The smell lives on the surfaces the dirty air passes over, and the bin is only one of them.
9. Let everything dry a full 24 hours before reassembly.Anything washed, including the bin. Reassembling damp is how a musty smell becomes a permanent one, and how a damp filter overheats a motor.
10. Deal with the cause, not the symptom.Scented pellets, a drop of essential oil in the bin, or vacuuming bicarbonate all mask a smell for a day and add residue to the filter. If a smell keeps returning, something in the machine is still dirty or still restricted.

Tips

• A quarter-teaspoon of bicarbonate of soda vacuumed up is the only masking trick worth using, and only on a machine that is already clean. More than that clogs a filter.
• In a pet household, halve every filter interval. Dander is fine, greasy and exactly what filter media holds on to.
• If the smell only appears after ten minutes of use, that is a heat signature and points firmly at airflow rather than at anything dirty.
• Wash the hose interior by running warm soapy water through it and hanging it in a loop to drain, then leave it a full day. A wet hose refitted is a guaranteed musty smell.

Common mistakes

• Continuing to use a machine with a sharp electrical smell — That smell is overheating insulation. Running it again to check risks a motor fire, and a machine that has reached that point is unlikely to be economic to repair anyway.
• Masking the smell with scented granules or oils — They coat the filter media and reduce airflow, which makes the underlying overheating worse. The smell returns as soon as the scent burns off.
• Refitting a washed foam filter the same day — It is not dry in the middle. That produces both the musty smell you were trying to remove and the restricted airflow that produces the hot one.

If it doesn't work

Questions people ask