Correcting case airflow and dust build up

[Scarly]

I have a Lian Li 216 case and I also bought a front dust filter for it. I have a few questions: I only have stock fans and they are set as follows: two fronts (160mm) at 20% (~620 rpm) and rear (140mm) at 20% (~460 rpm).
1 - Does this create positive pressure in the case? Even if I set rear fan at 25% I assume I will have positive pressure, am I right?
The dust filter also blocks some of the air. For my system I don't need really strong air flow, because I am fine with temps at 20% of speed, but I am worriyng about air pressure and less dust buld up. Besides, the lower the speed of the case fans, the less dust will pass through the case, right?
I also have my case on the floor right now and thinking about to put it on the table.
2 - Will this really reduce dust buildup?
I will be glad if you share your experience and advices!

 

[JWNoctis]

Welcome!

I have the exact same setup. There's no visible internal dust buildup after running under load 24/7 for a month - so actual case fan speed would have been higher, maybe 30-50% - though I do have an HEPA filter in the same room. I also had the top grille blocked out with printer papers since I don't use an AIO, and stuck another filter over the grilles to the right of the PCI slots. If you can feel air coming out of the gap above the rear fan, then it's certainly positive pressure.

In the end, it would probably depend upon how dusty your room is. I wonder why that dust filter did not come as stock with this case.

 

[joemama]

1. You've gotta test it yourself, find the gaps on the case and light a cigarette or something near it to see if the smoke gets sucked in. While the front fans are superior in quantity and size, the filter also brings in more resistance to air flow, so you can only guess without testing.
2. Positive pressure reduces the dust build up since air only goes in from the intake fans, which are usually designed with a filter. Otherwise unfiltered air would enter from any openings on the case bringing in more dust.

 

[Scarly]

Welcome!

I have the exact same setup. There's no visible internal dust buildup after running under load 24/7 for a month - so actual case fan speed would have been higher, maybe 30-50% - though I do have an HEPA filter in the same room. I also had the top grille blocked out with printer papers since I don't use an AIO, and stuck another filter over the grilles to the right of the PCI slots. If you can feel air coming out of the gap above the rear fan, then it's certainly positive pressure.

In the end, it would probably depend upon how dusty your room is. I wonder why that dust filter did not come as stock with this case.

Thanks! Yeah it is a shame they don't put the dust filter for default. I also blocked top panel. My room became dustier than before due to construction work outside =\
I just checked the air above the rear fan - I can feel small air (due to slow speed of fans I guess, only 20%).

1. You've gotta test it yourself, find the gaps on the case and light a cigarette or something near it to see if the smoke gets sucked in. While the front fans are superior in quantity and size, the filter also brings in more resistance to air flow, so you can only guess without testing.
2. Positive pressure reduces the dust build up since air only goes in from the intake fans, which are usually designed with a filter. Otherwise unfiltered air would enter from any openings on the case bringing in more dust.

Well, I made such test the other day: this case has a perforated panel under tempered glass along the entire length of the case. The smoke did not get drawn in there, it pulled back and went up, so I hope everything is right.

 

[chrcoluk]

Observations used what many will consider a dated case in 2024 (fractal define R4).

Two front 140mm intakes. Variable speed, (slow till CPU gets above 60C).
One rear exhaust 140mm. Variable speed, but will ramp up a bit earlier at 45C as its the only exhaust. This one is the most important, if I am doing something like full core cinebench for long time, it took a bit of effort to get a good fan here to prevent thermal throttle at 253 PL. But for daily use its no problem as CPU has never gone above 63C and usually sustained temps dont go above 45C.
One side 140mm intake. This to compensate for drive bays absorbing most of intake air flow from front.

I dont think I have ever compared temps with dust filter on/off, but I know if I open the door at front, its a noticeable impact. If this case had a removable door I was considering removing it, although the door has a big effect on the noise of the system as well, it absorbs a lot of it.

The dust filter does get lots of dust built up, even my exhaust area gets dust build up, this room is by far the most dusty in my home, and the area around my PC is especially dusty. For this reason I wont ever remove dust filters. The inside of case is very clean. Pretty much dust free.

Something I was reminded of when upgrading from 9900k to 13700k system, is how unrealistic test benches are for temperatures. My noctua heatsink inside case isnt hugely better than a bog standard stock style cooler on a cardboard box in the open, likewise my 9900k has no issues using a £15 fan whilst on a cardboard box, but in a case would melt with that fan installed. Exhausting hot air out seems more important than bringing cool air in with intakes.

I also finally got fan ramp up behaviour working better on this ASRock board, in case anyone in this thread cares, I had to use the GUI version of fan tuner in bios to get it right as I prefer stepped fan curves vs gradual fan curves.

 

[Scarly]

Observations used what many will consider a dated case in 2024 (fractal define R4).

Two front 140mm intakes. Variable speed, (slow till CPU gets above 60C).
One rear exhaust 140mm. Variable speed, but will ramp up a bit earlier at 45C as its the only exhaust. This one is the most important, if I am doing something like full core cinebench for long time, it took a bit of effort to get a good fan here to prevent thermal throttle at 253 PL. But for daily use its no problem as CPU has never gone above 63C and usually sustained temps dont go above 45C.
One side 140mm intake. This to compensate for drive bays absorbing most of intake air flow from front.

I dont think I have ever compared temps with dust filter on/off, but I know if I open the door at front, its a noticeable impact. If this case had a removable door I was considering removing it, although the door has a big effect on the noise of the system as well, it absorbs a lot of it.

The dust filter does get lots of dust built up, even my exhaust area gets dust build up, this room is by far the most dusty in my home, and the area around my PC is especially dusty. For this reason I wont ever remove dust filters. The inside of case is very clean. Pretty much dust free.

Something I was reminded of when upgrading from 9900k to 13700k system, is how unrealistic test benches are for temperatures. My noctua heatsink inside case isnt hugely better than a bog standard stock style cooler on a cardboard box in the open, likewise my 9900k has no issues using a £15 fan whilst on a cardboard box, but in a case would melt with that fan installed. Exhausting hot air out seems more important than bringing cool air in with intakes.

I also finally got fan ramp up behaviour working better on this ASRock board, in case anyone in this thread cares, I had to use the GUI version of fan tuner in bios to get it right as I prefer stepped fan curves vs gradual fan curves.

thank you for sharing your experience! For me, temps are not the problem, my system is pretty cold, so I'm only bothering about air pressure and, moreover, dust. You mentioned that your room is pretty dusty, do you have your case on the floor or on the table? And if the case was on the floor before, has the amount of dust on the table changed?

 

[#22]

I have a Lian Li 216 case and I also bought a front dust filter for it. I have a few questions: I only have stock fans and they are set as follows: two fronts (160mm) at 20% (~620 rpm) and rear (140mm) at 20% (~460 rpm).
1 - Does this create positive pressure in the case? Even if I set rear fan at 25% I assume I will have positive pressure, am I right?
The dust filter also blocks some of the air. For my system I don't need really strong air flow, because I am fine with temps at 20% of speed, but I am worriyng about air pressure and less dust buld up. Besides, the lower the speed of the case fans, the less dust will pass through the case, right?
I also have my case on the floor right now and thinking about to put it on the table.
2 - Will this really reduce dust buildup?
I will be glad if you share your experience and advices!

As you probably know, positive pressure is when more air comes to case than is exhausted. Hard to answer your first question, because every restriction like filter or grill reduces airflow of fan. And going lower with it's speed reduces not only airflow, but also static pressure. The lower the static pressure, the more airflow is additionally reduced by restriction. That's why it's impossible to give you clear answer by looking at numbers you gave above, but with suggesting with them and your case being not that restrictive even with (I assume) dedicated Lian Li's filter it's highly likely that your fans create positive pressure. Lower speeds obviously mean less dust if we compare all positive pressure setups. Filter and positive pressure of course will make a difference you will yourself notice. Sadly it's an airflow case, so worse in terms of dust protection and much will be coming inside thru the top opening. You can further reduce dust buildup by placing your pc somewhere higher.

I also finally got fan ramp up behaviour working better on this ASRock board, in case anyone in this thread cares, I had to use the GUI version of fan tuner in bios to get it right as I prefer stepped fan curves vs gradual fan curves.

You really prefer fan curves instead of e.g built-in fan controllers old Defines have? I personally hate fan curves and treat it as default solution for ones not controling things themselves, I mean average Joes.

 

[chrcoluk]

As you probably know, positive pressure is when more air comes to case than is exhausted. Hard to answer your first question, because every restriction like filter or grill reduces airflow of fan. And going lower with it's speed reduces not only airflow, but also static pressure. The lower the static pressure, the more airflow is additionally reduced by restriction. That's why it's impossible to give you clear answer by looking at numbers you gave above, but with suggesting with them and your case being not that restrictive even with (I assume) dedicated Lian Li's filter it's highly likely that your fans create positive pressure. Lower speeds obviously mean less dust if we compare all positive pressure setups. Filter and positive pressure of course will make a difference you will yourself notice. Sadly it's an airflow case, so worse in terms of dust protection and much will be coming inside thru the top opening. You can further reduce dust buildup by placing your pc somewhere higher.



You really prefer fan curves instead of e.g built-in fan controllers old Defines have? I personally hate fan curves and treat it as default solution for ones not controling things themselves, I mean average Joes.

I noticed was a fan switch on the R5 when building it not long ago (2nd rig in sig), but the connector for it wasnt easily accessible, I also prefer the idea of monitoring each fan independently which I am not sure is possible if they all shoved through a single fan controller.

I see pros and cons of both solutions but I think ultimately for me it would start to become tedious if i had to manually adjust fan speeds.

thank you for sharing your experience! For me, temps are not the problem, my system is pretty cold, so I'm only bothering about air pressure and, moreover, dust. You mentioned that your room is pretty dusty, do you have your case on the floor or on the table? And if the case was on the floor before, has the amount of dust on the table changed?

Case is on a very small table which is probably about half desk height.

I wouldnt put it on the floor, as an example my Xbox Series S is very low down, not on floor but on a very low open self just above floor, and that thing gets so much dust and even dirt particles its unreal, I only recently decided to get a cover to put over it.

 

[Bill_Bright]

I think joemama's simple explanation is the best explanation.

I will add a couple things.

1. When determining air flow, don't forget to factor in the PSU's fan "IF" it draws its intake from inside the case - as most top mounted, and a few bottom mounted PSUs do. Bottom mounted PSUs that have their own dedicated intake vent that exhaust directly out the back should not be factored in.​

​

2. Every filter will create some resistance to air flow. But that's fine. If it didn't, that probably means the filter is not fine enough to trap any dust. But note when clean, this resistance is very small. Even if packed with dust, a lot of air still gets through.​

​

3. I use and recommend Core Temp to monitor my CPU temps in real time. Under Options > Settings > Notification Area, I have mine set to display "Highest temperature" only. When I start to see my CPU go and sit above 60°C for more than a few seconds, that tells me it is time to clean my filters.​

Just from the description of your setup, it seems apparent you are creating a "small" amount of positive or overpressure. A small amount is good. Not enough or too much can create pockets of stagnant and heated air. Not good.

I would not worry about testing with anything that creates smoke. In fact, I would not worry about testing at all! Just use your computer for a few weeks, monitor your temps and see what happens. If you notice a bunch of dust building up in and around your USB ports, expansion card ports, rear panel I/O ports, and other cracks and crevices in your case, then you most likely have negative or underpressure (a slight vacuum) in your case that needs to be corrected.

It should also be noted that dust WILL still build up inside the case, even with that desired, slight positive pressure and air filters. But it will take much longer to built up to the point it should be cleaned.

No one can tell you how long those cleaning intervals should or will be. There are WAY too many variables and everyone's specific scenario is different. Older houses tend to be more dusty. The number of dander shedding humans and pets in the house are big factors. The number of rug-rats running around stirring up dust matter. Rugs, carpets, or bare floors matter. How often you clean your home, the type of HVAC filter, how clean the HVAC filter, the outside environment, the number of hours per day you run your computer, etc. etc. all factor in.

What I can tell you is, with my old unfiltered Antec case, and 2 adults, 2 kids, and 2 dogs in the house, I used to have to lug my computer outside for cleaning about every 4 months. With my filtered FD case, that immediately changed to about every 2 years - though I still had to clean my filters about every 3 - 4 months.

Today, with no kids or dogs running around, I clean my filters once every 6 - 8 months. But that's my computer in my computing environment. Your mileage WILL vary. I also clean my filters before they really need it. I learned if I waited until packed, I ended up making a mess dust-bunnies while removing them from the case.

I used to think side panel windows were just a fancy fad. After all, it is what's displayed on my monitors that's important. But all my case's must have a side panel window, if for no other reason than it is simple to, once a month or so, look inside to check on dust build-up and spinning fans without having to remove the side panel.

 

[Scarly]

As you probably know, positive pressure is when more air comes to case than is exhausted. Hard to answer your first question, because every restriction like filter or grill reduces airflow of fan. And going lower with it's speed reduces not only airflow, but also static pressure. The lower the static pressure, the more airflow is additionally reduced by restriction. That's why it's impossible to give you clear answer by looking at numbers you gave above, but with suggesting with them and your case being not that restrictive even with (I assume) dedicated Lian Li's filter it's highly likely that your fans create positive pressure. Lower speeds obviously mean less dust if we compare all positive pressure setups. Filter and positive pressure of course will make a difference you will yourself notice. Sadly it's an airflow case, so worse in terms of dust protection and much will be coming inside thru the top opening. You can further reduce dust buildup by placing your pc somewhere higher.

Thank you for your opinion! I totally agree with everything you said. In terms of dust filter, I tested my temps with it and everything was the same, like 1 degree difference, that's why I decided to reduce front fans speed. Before filter I had 25%, and I started to think that for my system this air is redundant (in lian li 216 fans produce a quite lot air even on small speed). So after I changed it on 20% I tested temps on Cyberpunk 2077 and it was the same. And after it I was bothering if I made negative pressure by this reduce

I wouldnt put it on the floor, as an example my Xbox Series S is very low down, not on floor but on a very low open self just above floor, and that thing gets so much dust and even dirt particles its unreal, I only recently decided to get a cover to put over it.

Yeah I definitely should put case on the desk.

Just from the description of your setup, it seems apparent you are creating a "small" amount of positive or overpressure. A small amount is good. Not enough or too much can create pockets of stagnant and heated air. Not good.

Thank you for your reply! Yes, as I texted above in this message, I wanted to find lowest fan speed + dust filter without affecting temps and then just wanted to make sure I didn't make negative pressure.

P.s. Now I am sure that I have positive air pressure (thanks to @JWNoctis with advice to check the air above rear fan on top panel. I felt air and decided to put a bit of cat's fur on the panel and it twitches on the air ahah), so now everything I can do is to put the case on the desk. Thanks everyone for amazing help guys!
Sorry for my english, I'm not fluent

 

[#22]

Thank you for your opinion! I totally agree with everything you said. In terms of dust filter, I tested my temps with it and everything was the same, like 1 degree difference, that's why I decided to reduce front fans speed. Before filter I had 25%, and I started to think that for my system this air is redundant (in lian li 216 fans produce a quite lot air even on small speed). So after I changed it on 20% I tested temps on Cyberpunk 2077 and it was the same. And after it I was bothering if I made negative pressure by this reduce

Advantage of high airflow cases is their unobstructive construction giving oportunity to largery slow down the case fans without loosing that much performance. And any rig needs given amount of performace when providing it more results in dimnishing returns - your 1C example. That's why maybe it's not the best case to protect from dust, but you can use mentioned advantage to pull lest dust and lowering noise of case fans. With noise it ofc stops making sense when anything other becomes louder and during summer components will go crazy due to high ambient temperature you can't fight with airflow, but it's worth to experiment in case of finding the best speeds for your likings.

EDIT: Forgot to mention, better don't experiment with all kind of smoking stuff and airflow visualisation. Computers don't like them and definitely hate these wet types of smoke like e.g. one coming from this things people smoke instead of regular ciggarettes. I don't know how it's called in english, but you know what I mean - fancy smelling, flavoured shit being here for maybe a decade, so still tested on people and people liking it.

 

[Vayra86]

At lower RPM, you can also add a bottom intake if the case allows for it, I've had positive results with that especially now that there's more wattage going through a system. Two intake 1 outtake is getting a bit too light these days. This is a better move than going for higher RPM - that is if you have a dust filter on the bottom too, otherwise its not recommended.

 

[Scarly]

Advantage of high airflow cases is their unobstructive construction giving oportunity to largery slow down the case fans without loosing that much performance. And any rig needs given amount of performace when providing it more results in dimnishing returns - your 1C example. That's why maybe it's not the best case to protect from dust, but you can use mentioned advantage to pull lest dust and lowering noise of case fans. With noise it ofc stops making sense when anything other becomes louder and during summer components will go crazy due to high ambient temperature you can't fight with airflow, but it's worth to experiment in case of finding the best speeds for your likings.

Yeah it was legit tests due to summer time, now I have hell weather so I was glad to test it now. Now I have my preferred fan speed/perfect case sound/nice temps.

About smoke tests its understandable. I just did it once and no smoke went through case, then I ventilate my room immediately.

At lower RPM, you can also add a bottom intake if the case allows for it, I've had positive results with that especially now that there's more wattage going through a system. Two intake 1 outtake is getting a bit too light these days. This is a better move than going for higher RPM - that is if you have a dust filter on the bottom too, otherwise its not recommended.

Tbh I don't now how LOW my case RPM's really are compared to other cases, because I heard many opinions that this case has high fan speed even when they are quite low. Plus front fans are 160mm.

 

[Bill_Bright]

Do be advised that when it comes to hair and dander, cat is by far, the worst in comparison to dogs and humans. Cat hair and dander tends to be more oily and sticky than dog and human. And when mixed with "normal" house dust, it coats the interior of your computer and all the components. Over time, this heat trapping blanket of dander, hair, lint, dust, microscopic critters (dust mites) that eat that dander, dust mite poop those critter excrete all over the place , and whatever else that floats around in dust getting drawn into the computer, thickens and becomes increasingly difficult to clean.

I just had a sneezing attack thinking about that.

Depending on the number of people and animals and other dust producing factors, this build up can happen quickly.

I recommend all users get into the habit of routinely inspecting their filters for build-up and cleaning as necessary. I would start at once a month until you determine the correct interval for your specific scenario. But note in the warmer months, windows and doors are opened more often, people and pets come in and go out more often, all of which allows more dust in.

If there are smokers in the house (quit!) and/or a lot of kitchen grease/oils in the air added to this mix, it can get to the point that layer of heat-trapping, gooey dust almost takes a hammer and chisel to scrape off. Now for sure, I am talking about years of neglect but I hope this illustrates to all reading the importance of having decent, removable, "washable" filers. Don't buy a case without them - even if it is just you and your goldfish.

 

[Vario]

Just get a Metro DataVac or similar duster and blast it out every 3 months and stop caring about dust the rest of the time.

I don't run filters on any of my computers they have almost no dust. If they do it gets blasted out anyway.

 

[#22]

Yeah it was legit tests due to summer time, now I have hell weather so I was glad to test it now. Now I have my preferred fan speed/perfect case sound/nice temps.

About smoke tests its understandable. I just did it once and no smoke went through case, then I ventilate my room immediately.


Tbh I don't now how LOW my case RPM's really are compared to other cases, because I heard many opinions that this case has high fan speed even when they are quite low. Plus front fans are 160mm.

The problem with mentioned stuff to smoke is it comes to your pc as smoke, but then sits on whatever and changes into liquid what may kill components. I don't exaggerate, it's a classic of pc repairs. Short experiment was fine, but generally avoid smoking whatever in room where pc works.

About low RPMs, my must is pc simply inaudible during low load like webbrowsing and for all of this time, so no rapid ramp ups, because something got hot for a second. But it starts with needing to have fans capable of running like that or running passive. Totally recommend, even if it means buying replacements. It's just bad to have it different nowadays when we came so far from damn loud 00's computers with all of the noisy stuff you could at best mitigate with sound-dampened cases.

 

[Bill_Bright]

Just get a Metro DataVac or similar duster and blast it out every 3 months and stop caring about dust the rest of the time.

Funny how some people assume their scenario automatically fits everyone.

If only it were that easy for everyone.

My mid-tower FD case weighs 24lbs - empty.

Add motherboard, CPU, CPU cooler, RAM, 3 drives, graphics card and now its a big, bulky box that weighs over 35lbs.

Plus it slides into a cubby-hole slot in the bottom of my desk. It has 1 power, 2 audio, 2 HDMI, 1 Ethernet, and 4 USB cables.

I am not a young man. While I am physically fit (I ride a bicycle 25 miles every day it is above 60 and not raining), it is still a genuine PITA and physical challenge for me to tear down my system then lift and lug that box outside to blast out the dust.

Oh, and I have 4 PCs in the house so again, funny how some people just assume their scenario fits everyone.

But don't worry, Vario, your day will come. Days may drag on, but the years fly by.

 

[Vya Domus]

My advice to you and this is what I also do is : buy one of those dust blowers and just clean your PC every once in a while and get rid of those dust filters which just block airflow and the dust gets inside anyway.

 

[Bill_Bright]

Nonsense.

Dust filters do NOT "block" airflow. And if case flow is setup properly, only a tiny percentage of the total dust gets inside.

The difference is hugely significant from having to clean the interior once every few months to once every few years!

 

[P4-630]

Dust filters do NOT "block" airflow.

Depends on what kind of "dust filters" you use.

 

[Bill_Bright]

Depends on the actual "dust filters" you use.

Come on! Let's be realistic and not pedantic here, and try to be helpful for the OP and future readers, okay?

We are talking about "PC case air filters". Show us a PC case air filter that is designed to block air (block, as to prevent all air flow) as well as filter dust.

 

[nguyen]

The dust filter on my corsair 5000D caught a lot of dust, so I clean it every 2 months, dust inside the PC is minimal after 1.5 years of usage

I use high static fans Phanteks T30 and it suck air through the dust filter just fine, normal airflow fans will have air pressure significanly reduced though

 

[Vario]

Funny how some people assume their scenario automatically fits everyone.

If only it were that easy for everyone.

My mid-tower FD case weighs 24lbs - empty.

Add motherboard, CPU, CPU cooler, RAM, 3 drives, graphics card and now its a big, bulky box that weighs over 35lbs.

Plus it slides into a cubby-hole slot in the bottom of my desk. It has 1 power, 2 audio, 2 HDMI, 1 Ethernet, and 4 USB cables.

I am not a young man. While I am physically fit (I ride a bicycle 25 miles every day it is above 60 and not raining), it is still a genuine PITA and physical challenge for me to tear down my system then lift and lug that box outside to blast out the dust.

Oh, and I have 4 PCs in the house so again, funny how some people just assume their scenario fits everyone.

But don't worry, Vario, your day will come. Days may drag on, but the years fly by.

I don't lug it outside, I just blast it out in the room and then vac up the dust.

My advice to you and this is what I also do is : buy one of those dust blowers and just clean your PC every once in a while and get rid of those dust filters which just block airflow and the dust gets inside anyway.

This is the way. Dust filters just reduce air flow and increase fan noise, you don't need them. A thin layer of dust won't harm your shit and you can just blast it out regardless. Back in the day there weren't dust filters on stuff and yet it still worked fine. Its a gimmick. Dust builds up on the filter and then you have less air flow and your components run hotter.

I actually haven't used an airduster in over a year, I have no filters on the case besides the case grills and here is how much dust I have:

I also have 4 desktop PCs, all are filter less. I don't have any pets nor do I smoke, so your mileage may vary. I don't think its worth even worrying about.

 

[P4-630]

Such as this I used in the past with a LianLi case, NO dust gets inside.

With all other standard PC "dust filters" you will get dust inside your case.

 

[Bill_Bright]

I don't lug it outside, I just blast it out in the room and then vac up the dust.

Well, if you don't mind much of that dust getting tossed up into the air again where it goes up your nose, into your eyes and back into your case, that is your choice.

Dust filters just reduce air flow and increase fan noise

Yeah - if you neglect cleaning, allow them to get packed with dust before you finally do clean them, that is true.

FTR - I hate fan noise. I mean I really hate it - this goes back to my first love in consumer electronics - audiophile quality audio reproduction where any fan noise was unacceptable.

So the solution for PCs is simple. Use large (140mm or larger), quality case fans in a quality case. Fractal Design Define series cases are great for this. Quality fans included with sound deadening lining throughout the case. Total silence the majority of the time. In fact, any fan noise I do here is from the CPU and GPU coolers when they ramp up - and occasionally, from the PSU fan.

Such as this I used in the past with a LianLi case, NO dust gets inside.

Right. But air still gets through. It does not block air too.

If folks don't want to use filters, that's fine. But folks need to stop suggesting they don't work as that just is not true.