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Robot vacuum cleaners might give the impression that to do a good job cleaning a floor, all you need to do is cover the whole floor area and you're done. This is clearly untrue to a competent human vacuum operative, and the results of competent human vs robot strongly suggest that the human is correct.
So what's going on?
Perhaps surprisingly, using a vacuum is a multi-sensory experience. We can see areas with dirt and assess after one pass how well we did cleaning that spot. But, in addition, we can also hear how much dirt the vacuum is picking up. This is particularly easy with something dense/hard like sand or bits of cat litter, there's a satisfying tinkling sound as the particles bounce off the walls of the tubes. This means we slow down our coverage to ensure better cleaning, or perhaps go over the area a few times to make sure we got as much dirt as possible. Unfortunately, this system doesn't work with finer dust that might be too small/light to be heard or seen.
To solve this, a particle counter, like those seen in air quality monitors could be included in line. Now, we get a read out of the fine dust being picked up by the vacuum. So, now we know if an area is still dirty after one pass or not.
The_20Stillness_20of_20Dust
[xenzag, Jun 12 2023]
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Whoa, so you'd have a meter on the handle moving from dirty to clean, just go over the area till you move that needle into the latter. Nice. [+] |
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OK, looks baked. It's a fair cop. |
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Been there...(link)... just add the counter... |
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Fewer particles could represent a cleaner floor, but they could also represent heavier, stickier dirt. |
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//inspired by some high end particle counting equipment in a clean room?// |
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If only. Labs are built in one of two ways, negative or positive pressure. Negative pressure is conventional for chemistry labs, among others. It's created by the presence of one or more fume hoods which take air from inside the lab and vent it to the outside. This means any nasty fumes from any chemical reactions you may be performing go straight out and not back into the building where they may harm a student, useful employee or member of HR. |
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Positive pressure labs and other facilities such as operating theaters, take outside air, filter it and push it into the lab space. This means general contamination like dust is continuously moved out of the area. This means that maintaining biological sterility is much easier. The same is true for sensitive manufacturing processes. You can also hybrid this with positive pressure and negative pressure zones. |
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My lab has a need for biological sterility and also has certain chemicals in large enough volumes that could be a problem if dropped on the floor violently enough. So which way did the powers that be decide to go? Pure negative pressure. It's cheaper, and the fire people REALLY don't like forced air intakes. But, it means the whole lab fills with dust. |
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Lab cleaning is a sticky subject. Building cleaners won't touch it, because they don't know what they're dealing with. There's no budget for cleaning supplies in any given scientific grant. If cleaning supplies are spotted in labs it triggers issues with the union of the existing cleaning staff. Then, who wants to spend time cleaning in an extremely competitive academic research environment? The upshot is that it rarely gets done and a lot of research labs are dirty as hell. |
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//Fewer particles could represent a cleaner floor, but they could also represent heavier, stickier dirt.// |
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Conventional air particle counters separate out into <10um, <5um and < 2.5um, so there is some accounting for this. I'm a Miele vacuum fan and quite pleased with how little particulates it puts out compared to my previous vacuum. Highly recommended. |
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Surely a weight indicator would be a more reliable measure of cleaning effectiveness, due to the wide disparity in particle size. |
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No, it needs a multi-variable approach, otherwise if you accidentally vacuum up something reasonably heavy, like a dirty sock someone has abandoned on the floor, the vacuum cleaner will conclude that the floor must be spotlessly clean |
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//Surely a weight indicator would be a more reliable measure of cleaning effectiveness,// |
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How would this work? Are you suggesting measuring the mass of the airstream or the bag/receptacle? That's all going to be tremendously unworkable as you'd need to reference the rate of change to floor area covered. That mass/weight change is going to be tiny compared to the forces generated by the vacuum/airflow. |
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What would prevent people from cheating, though, by scattering dirt around first and skewing their results? Everyone's so competitive. |
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