Thread: Vacuum cleaner issues

These graphs are from some vacuum cleaner testing I did back in 2012 and seem to have had their image links broken s0 I thought it might be a timely reminder about vac issues.

This testing also shows why vacs that filter the motor cooling loop air are better than those that don't.

The test involved a near new high end HEPA filtered Vac in excellent condition - the motor was cooled by a non-filtered air cooling loop.

The results for the air exiting the vacs HEPA filter showed nothing unusual (all >99% efficiency) when used with;
- a used dust collection bag
- a new dust collection bag
- a ROS sander with 240 grit paper.

After ~2 minutes of sanding I stopped the sander and Vac and measured the dust levels in the air ~1m away from the sander.

The graph immediately below shows the % decrease of the dust in the shed air for a range of particle sizes.

The (negative decrease) INCREASE for the <1 micron dust is unlikely to be cause by filtration issues on this vac as the HEPA filter does remove >99% of the dust that passes through it. The vac is even effectively removing the coarse dust from the general shed air which is something I have seen before with well sealed DCs. A more likely explanation for the increase in fine dust in the shed is the sander/vac combo was not catching all the fine dust generated as easily as it catches the coarser particles so the fine dust levels build up in the shed air. Simple enough.




I then ran the vac without the sander and measured the dust in the air coming directly out of the motor cooling loop and compared that to what was in the shed air.



What this shows is the motor cooling loop was continually making fine shed dust into finer dust, increasing the shed air background for the finest dust by up to 50 times. this might also at least partially explain the previous graph up top.

The motor cooling loop dust issue could be a double whammy.

If you live in a cleanish area and your shed is well vented with good fine dust capture then very fine dust may be very low (ie 0.1 ppb). Raising this by 50 times is only 5 ppb, so nothing to worry about.

OTOH if you have no ventilation and no or limited fine dust collection and your shed fine dust levels are around 10 ppb, then continual running a vac whether you are actually using it with a tool or not or not may eventually turn 10 ppb into 500 ppb of the most dangerous dust. This is not so good.

Solutions:
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Best practice would be a ducted vac system with the Vac either enclosed in an air tight enclosure inside the shed and vented, or located outside.

If you already have a vac and don't want to buy another or upgrade your fine dust collection then ventilation may be a cheap solution since it solves both the un-captured fine dust and the motor cooling dust generation issue. The ventilation must be forced (no relying on sea breeze or whirlybirds) You should target ~20 room air changes per hour.

Using a vac that filters its motor cooling loop solves the motor cooling loop dust maker problem but not the escaping fine dust problem. nevertheless if you are about to buy a new vac then a vac with a filtered motor cooling loop will help. Unfortunately not many vacs do this but according to Lappa the $75 Kmart cyclonic vac does and I know our Dyson cordless does as well.