Getting rid of dust from home and from a computer case

Dust is something not welcomed and the more dust gets to a room or to a computer PC the more often it has to be cleaned. For quite some time I was noticing a much higher dust buildup in my home that in few offices closer to the city center so I've decided to investigate this mystery. Here is my investigation involving air quality sensor, air purifier and winter heating season.

Quiet and green neighborhood - nothing that would imply a high dust concentration in the air

The usual place for visible dust buildup was the display. With the correct light angle it's easy to see on dark matte surface. I also had a fan used for cooling/ventilation that was sucking air from an open window into the room. The blades were getting covered by a dark dust-like deposit. It was coming from outside.

Dust getting on the display

That wasn't the most affected places and things like a display are easy to clean. I'm using Fractal Design cases with dust filters and they did work, having some dust to clean with a vacuum cleaner every week or two. However inside there wasn't any macroscopic dust but rather a fine layer of ash-alike dust. In my current PC using two 240 radiators with fans set to exhaust from the case giving negative pressure inside the ash-alike dust buildup was even more noticeable as air getting in was bypassing dust filters. The power supply did pull the air through a dust filter and it did caught some dust but the fine one did pass through. Something was not quite right - where this fine dust is coming from?

Dust inside my computer pulled through unfiltered openings due to negative pressure in the case

Fine dust pulled into the power supply

Dust on the PSU dust filter

The next step was to get some tools for further analysis - so in this case it was an air quality sensor. I picked a Temtop P600 device locally. It measures PM10 and PM2.5 particulate matter in air - a fine dust that you can breath in and which can have negative effect on your health. Smoke or smog are an example of such fine dust . In Poland for PM10 daily concentration of 50µg/m3 is acceptable, 200µg/m3 is notice level and 300µg/m3 is alarm level. EU gives 50µg/m3 daily and 40µg/m3 annually as acceptable for PM10. For PM2.5 25µg/m3 is acceptable annually.

First in-home measurements indicated 15µg/m3 for PM2.5 and bit more for PM10. That's not bad and I started to look for potential sources of higher PM values. I tested my vacuum cleaners. The new one when used or when the sensor was put into the exhaust air showed only bit higher dust concentration. The old one directly in the exhaust air showed 50-60 µg/m3 and up to 100µg/m3 for PM2.5 - which could be expected as the air did have that dusty scent (and it's the reason why it's not used any more). Those filters many vacuum cleaners have are there for a reason.

Bad vacuum cleaner may spread some settled dust into the air but the dust must first enter the room (especially when I ventilate all rooms when/after cleaning). There must be some sources of fresh dust.

Old vacuum cleaner spreading a lot of dust

Here in Warszawa, Poland central heating is used to warm houses during winter. Big plant generates heat and distributes hot water through the system. In smaller cities or city blocks where such system isn't available people use their own personal heaters burning coal, wood or even trash, plastic etc. Depending on the heater or fuel quality the exhaust gases can contain lots of dust, smoke, ash and harmful compounds. That's the reason why some cities get smog in winter (it doesn't have to be cars and alike).

As my house is near a forest and is on the edge of the city I expected good air quality, but during some nights I was able to pick a faint smell of something burnt, like from kitchen. I was curious what the air quality sensor will show if such night would repeat.

The night air quality measurements differed night from night - different air masses, wind speed and direction etc. During day PM2.5 was usually around 10-25µg/m3 and bit more for PM10. During nights the quality was worse - 35-45µg/m3 seems average - heating season, day-night cycle? Hard to tell based on this measurement alone.

But the night with the something is burnt smell did reoccur. The PM2.5 was reaching 100µg/m3 and PM10 up to 125µg/m3 - now that's a shocking result. It could be a specific wind direction dragging exhaust gases from a bad heater or from some industry facility. Hard to tell.

When air has weird burnt smell something is not right

It will be important to measure the air quality during spring/summer to see if night air quality gets better or if those burnt-nights reoccur when house heating isn't used. There were already nights with good to very good air quality.

One of rare nights with better air quality

And one night with excellent air quality

Having those measurements in hand I started taking actions. First was to not ventilate rooms at night when outside liquid death is flowing - trying to do that before night comes with it worse air.

And if it's dust then hard spring cleaning are in order to limit the existing dust amount. I did try to clean every odd place like top of shelf and furniture to be sure there is no dust concentration in every room and so on. Even when cleaning windows the dust when wet was quite black in appearance. Was it sooth-like dust from those heaters?

And when everything solid is cleaned then the air cleaning remains - I picked up an air purifier to keep the air inside as clean as possible.

I started researching air purifiers - what are the good models in not so steep prices, what features are marketing and which one are important. Pretty much every vendor bombs you with scary bacteria, fungi or viruses not to mention dust, evil dust.

Initially I had purifiers with ionization feature or a HPP based filter - but I decided to skip those as I really didn't wanted ozone and it smell. It's a harmful compound and ventilating a room to get rid of it isn't the goal for freshly cleaned air in a room. Also germ-free marketing isn't that much of a reality in practice. Aside of that the replacement filters should be easily available at acceptable price and the device itself should work efficiently, have good reviews and shouldn't be loud if not set to high throughput.

So I picked Xiaomi Mi Air Purifier 2S - it has high enough throughput to handle my room, replacement filters are all over the place and it has good reviews and relatively low price. The device has a night, automatic and favorite modes. Night mode keeps it at very low RPM, auto mode scales RPM with air quality and favorite sets custom RPM - either max or what you set with the Xiaomi mobile app. The auto-mode is silent below 20µg/m3 and gets only slightly louder above that threshold. It will go even faster at higher values. The maximal fan speed is quite loud but it's rather a monotonous sound so you can handle it for a short moment if needed.

Average air quality before air purifier was put to use

When I'm in the room I run the air purifier in auto mode. When I'm off to work I set it to max to clean the whole room/house. When I'm back the air quality sensor shows around 3µg/m3 (where as direct exhaust from the purifier is below 1µg/m3). The PM2.5 rises during nights with bad air quality, especially if I open a window for a moment - but it doesn't go above 20µg/m3.

The air is really clean when I'm back from work

Xiaomi Mi Air Purifier 2S does work as intended

It's hard to tell quantitatively if the amount of dust on for example the display lowered - but it does look like. Dust is still on the display, on the table etc, but like less. I also have a PC on an open test bench right now and it also seems to stay mostly dust free. More definitive answers will come after a much longer period of time. I'm still looking at potential source of dust that is still showing up.

Less dust is not only the air purifier work. Analyzing the problem led to change of behaviors which may also play a role. Also the after period wasn't quite long so there may be still some short term variations or long term trend. As of now it looks positive.

As for other possible sources there could be some in-home like say an old paint or things like antiperspirants that do trigger both air quality sensor even when I use them far away or on the balcony...

I'm planning to continue the measurements to see how air quality will change during warm nights. Also long term effect of air purifier and better cleaning is on the radar. Looking at the air purifier filter right now it does catch some dust so with time dust available in house could start decreasing.

I'm also doing some fan rearrangements in my PC to have a positive pressure and air coming through dust filters only. I may also try HEPA paper filters if I find a right variant.

To end this story some of my ideas or things that should be done to avoid dust in a PC. Some are just good practices, some things to look out when building a PC - like positive pressure inside, while others are my ideas that might help.

If air goes through a HEPA filter it will catch even the very fine dust. That what air purifiers do. The problem is that those filters impose a very high air drag and most case fans would not be able to handle it. SilverStone still likely offers Mammoth Series MM01 case with such filters built in - it's not small, quiet or cheap. If you would want to mod a HEPA filter then it would have to have the right size to tightly seal the air inlet and the fans would have to be optimized for static pressure rather than for high airflow.

More realistic idea could be with HEPA paper-sheet filters. You can cut a sheet to size easily and the G, F, H filters stop smaller and smaller dust particles at an increasing air drag. Using more static pressure optimized fans at less aggressive fan curves could work. I have a H-filter (stops even the smallest dust particles) and with a quick test with a Noctua NF-S12B it still allows some airflow but much less than when the filter did not use any filter. Trying a HEPA filter from a small air purifier gave practically no airflow.

HEPA filters are very effective but put high air drag

Thin paper sheet HEPA filters are easier to use and put much less drag

HEPA filters are designed to stop very fine particles

Air will go through the path of least resistance so if using such filters the whole air inlet area must be covered tightly with such filter or air will bypass it. Even when using a normal case with normal case dust filters you have to have a positive pressure inside PC case so that you won't have missing airflow coming through non-filtered holes. If needed you would have to add one or more extra inlet fans. You can check video below to learn more about it.

Getting positive pressure in a PC case may require adding more inlet fans

Due to gravity dust will accumulate on the floor. PSU or case fans may be then able to pick it up increasing the rate at which dust builds up. You can keep your PC on your desk or use hooks to have it hanging below it but further away from the floor. There are even simple caddies on wheels that help moving PC cases - that's few centimeters extra from the floor and easy movement allowing cleaning the floor below the PC at the same time.

PC case caddy can be handy for moving a PC and to clean below it

Passively cooled low power CPUs can be installed in cases with no fans. No direct airflow limits the amount of dust that can settle down. However many of such cases have a lot of ventilation holes. That's bad, but there are alternatives. Some cases are designed to function as a radiator and do not have nearly any holes. Such cases are made by for example Akasa and Streacom. You will have to pay extra for such cases and you won't be able to put the most power-hot-hungry components (it depends...). There are even passively cooled GPUs like GTX 1050Ti KalmX or some rare RX 460/560 models.

Akasa PC-case-radiator looks pretty and blocks dust from getting inside

Streacom DB4 can handle bit more power hungry components

There are open cases like Thermaltake Core P3 and P5 or open test benches. Those can catch some dust settling down from above them. An air purifier exhausting clean air up above them could prevent that. In more traditional cases where you can have air inlet on the front panel you would have to have an air purifier in front of your PC blowing clean air at it - and at that point it becomes more practical to just clean the air in the room with a powerful enough cleaner.

And even with the best air purifier there always will be some dust. Regular cleaning is the most reliable way of having a clean room and a clean PC ;) Just get a can of good compressed air (which isn't air on average) that doesn't leave oily traces and blow through any dust.

Or maybe you have your own methods dealing with dust?

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