PanasonicVac
The point of the fog test is to test how well vacuums can filter and seal allergens that are 5 microns or bigger (particles that you can see with the naked eye). If it can't filter 5 microns or below, then what makes you think it's going to filter anything smaller? Sure, air purifiers are good machines for keeping good air quality, but I wouldn't want to rely on them (or the HVAC) solely for keeping the air clean.
The dump-out bags needing to be washed out does not help your point. Maybe my school's janitorial staff was negligent in terms of maintenance, but washing the bags just creates more downtime for when they're washed and dried. You could buy an extra set of dump-out bags, but at that point, you could do the same thing with a decent bagless vacuum, and probably get better filtration.
Now, can we get back to the thread's original topic, or do I need to defend myself again?