Stefan Stojanovic

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Stefan Stojanovic

Stefan Stojanovic

@PlasticFull

CEng PhD test development engineer. Learning about air cleaner design. Tweets,RT,♥=Opinion ❌Endorsement/professional advice Mastadon @[email protected]

UK Katılım Eylül 2020
1.6K Takip Edilen2.1K Takipçiler
Stefan Stojanovic
Stefan Stojanovic@PlasticFull·
@CleanAirStars @mishwoz @CleanAirClassrm @DouglasBooker @nathan_wood_8 @hugx4pets @BESAGroup @EllaRobertaFdn @HenryBurridge @CamdenCleanAir @KAPlastics @ventilationpro @JimRosenthal4 @CorsIAQ @jljcolorado @MumsForLungs @robwiss Yeah they will be higher resistance than Filtrete mpr 1900. Lower cadr. Larger difference between smoke and dust/salt cadr. Slightly higher noise than Filtrete. Min speed of that fan would be same as vent axia fan on max speed >50dba. Can be sourced from JASUN filters in UK.
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Stefan Stojanovic
Stefan Stojanovic@PlasticFull·
@adsquires Faced choice as teen with friends in car. Brakes failed leaving motorway. Happened so fast. Engine breaking & handbrake not enough 📉 Ditching was terrifying, costly, friends confused, screaming 😱 Bruised, no complaints after. Better than stopped cars or roundabout t-bone.
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Adam squires
Adam squires@adsquires·
You shouldn't downplay what smashing into the car in front would have looked like, just because swerving into a ditch isn't nice.
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Adam squires
Adam squires@adsquires·
Since we are seemingly having a "pro-lockdown" / "anti-lockdown" debate, this is what I think.
Adam squires@adsquires

@SGriffin_Lab @AdamBienkov Lockdown is like swerving into a ditch when your brakes fail, to avoid hitting the car in front. Truss is vowing never to swerve into a ditch, but not to get the brakes fixed.

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Stefan Stojanovic
Stefan Stojanovic@PlasticFull·
@DavidElfstrom @sri_srikrishna @AltenbergLee @built_envi Face velocities vary greatly across the panel too. Highly non uniform. Biased to one side typically and show patterns that indicate static pressure waves that I think are driven by fan blade passing frequency and quarter wave resonances. Best to test whole unit at sub micron.
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Devabhaktuni "Sri" Srikrishna
Devabhaktuni "Sri" Srikrishna@sri_srikrishna·
CLASSIC + GREATNESS: A 2019 paper (pre-pandemic) by Illinois Institute of Technology (IIT) researchers addressed most fundamental question during pandemic: which MERV 13 HVAC filters actually work well at sub-micron particle sizes? (Some don’t) (1/11) built-envi.com/wp-content/upl…
Devabhaktuni "Sri" Srikrishna tweet media
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Stefan Stojanovic
Stefan Stojanovic@PlasticFull·
@SprkJoy4BtrDays @PeteUK7 @SharonBurnabyBC Simple answer is mini purifiers are far from ideal shaped like a traditional purifier/Cr box. Unless in a small space like a car. Best to blow at you, through a filter, if flow is low. Qt3 is ok for that. Will share test results of cheaper slim & short, plug in builds soon.
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🌻Ms. Heref Oryou
🌻Ms. Heref Oryou@SprkJoy4BtrDays·
@PeteUK7 @SharonBurnabyBC Gotcha. Whenever the crew gets around to it…it would be super helpful and timely to have a comparison of the QT3 vs a DIY mini CR box VS a smaller filter that would be used with an extension cord.
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Tom Marshall
Tom Marshall@TomPMarshall·
@fearnley_k @KateCushing2 @guardian Covid & 2.8 million more out of work. Colleagues in UoB hoping to look into this. Various possible contributors: 1) post-Covid symptoms 2) Mental health problems following pandemic 3) Health care system problems (eg: people on waiting lists; delayed diagnosis/treatment)
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Stefan Stojanovic retweetledi
Billy Hanlon
Billy Hanlon@bhanlon15·
"YouTuber "Physics Girl" dealing with long COVID as her sister helps from Denver" "I can't talk...I can't move," said Cowern in a video on Facebook" @thephysicsgirl msn.com/en-us/health/m…
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Stefan Stojanovic
Stefan Stojanovic@PlasticFull·
@ianwrob @DavidElfstrom Think it's todo with fake reviews. Not sure. This purifier is rebranded under many names anyway. Like Russel Hobbs in UK. Good feedback. All from same original manufacturer's. I've tested it personally, passed data to @CleanAirStars and have donated to family and schools.
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Stefan Stojanovic
Stefan Stojanovic@PlasticFull·
@SmartAirFilters @PeteUK7 @EPA Will be case specific & need testing. It's so complex in terms of flow dynamics that can't make generalisation between different geometries. Why CFD used to model and tweak designs for HVAC applications. Eg vane axial tube fan (cannon) & simple axial (box) fan v different.
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Smart Air
Smart Air@SmartAirFilters·
@PeteUK7 @EPA It'd be neat to see other combos compared on inlet versus outlet. That simple setup was the only one that I found that had direct comparisons of inlet versus outlet.
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Smart Air
Smart Air@SmartAirFilters·
10 years ago, I built a DIY air purifier, and people rushed to tell me I was an idiot because I put the filter on the front. 😂 Obviously it should go on the back! New study from @EPA finds filter on front slightly outperforms. 👍 onlinelibrary.wiley.com/doi/full/10.11…
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Stefan Stojanovic
Stefan Stojanovic@PlasticFull·
@RealSexyCyborg Hard to spec test without a threshold. Id guess standard purifier test chambers going to be difficult to differentiate residual environment particulates vs shedding at low p/cm3. Needs recirculation to be representative. True clean room / environmental chamber could maybe do it🤷
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Naomi Wu 机械妖姬
Naomi Wu 机械妖姬@RealSexyCyborg·
@PlasticFull Logistics are a separate issue, I think saying it doesn't need to be tested is a problem. We had studies showing GUV SOCs weren't an issue either- fortunately no one stopped with that and now we have more studies to look at that show we need to take a closer look.
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Naomi Wu 机械妖姬
Naomi Wu 机械妖姬@RealSexyCyborg·
Uhh, I'd kind of thought that microplastics being released in any significant quantity from high volume filters were a fairly remote possibility but the number of people who feel it's absolutely imperative that not even cursory testing ever take place has me a little worried😕
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Stefan Stojanovic
Stefan Stojanovic@PlasticFull·
@RealSexyCyborg Not sure how to test it without equipment like ashrae has. Will have to dig into literature. I know in my rough chamber, plantower neph reads zero across all particle counts eventually with filtrete. But that's orders of magnitude higher than ashrae paper p/cm3 resolution.
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Naomi Wu 机械妖姬
Naomi Wu 机械妖姬@RealSexyCyborg·
@PlasticFull Well, since high ACH levels through large filter surface areas is what they are going to come at, best to have data on exactly that ready to refute those objections. They'll work other angles, but no reason to leave any low hanging fruit for them.
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Stefan Stojanovic
Stefan Stojanovic@PlasticFull·
@AltenbergLee @sri_srikrishna @JbcLiftec tested aerostar in EU and found high filtration Vs spec on a flat piece of material. High resistance though, very coarse pleats and glue at edges came away easily. I wouldn't recommend them.
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Lee Altenberg, Ph.D. 🇺🇸
Lee Altenberg, Ph.D. 🇺🇸@AltenbergLee·
@sri_srikrishna I've bought AeroStar but I've never seen them rated. We need a "filter nerd" like the "mask nerd" to test all the different filter brands to see how they perform. I nominate ... :)
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Stefan Stojanovic
Stefan Stojanovic@PlasticFull·
@RealSexyCyborg Wonder if it's single radial blower open both sides? Trend of quieter high flow units designed that way. Open both sides radial blower means higher flow, less prone to high pitch resonating, but typically lower pressure capability. Which 2 filters compensates for.
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Naomi Wu 机械妖姬
Naomi Wu 机械妖姬@RealSexyCyborg·
It's also worth mentioning that the frequency of the SA600 fan noise is a tad lower and more throaty than my Xiaomi. I have pretty high levels of background noise at home but anything with a high-pitched whine goes straight in the trash. SA600 is good in that regard.
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Naomi Wu 机械妖姬
Naomi Wu 机械妖姬@RealSexyCyborg·
New @SmartAirFilters SA600 just arrived, e-thot for scale😁 Purchased, not a review unit. So far- very well designed, no app nonsense, intuitive controls, excellent build quality. Filters were easy to pop in (pulls air from both sides).
Naomi Wu 机械妖姬 tweet mediaNaomi Wu 机械妖姬 tweet media
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Stefan Stojanovic
Stefan Stojanovic@PlasticFull·
@RealSexyCyborg Wonder if there are studies on MERV in similar way with pre cleaned air. There are different design points for Merv vs HEPA in terms of pressure vs flow. CR box is much lower than typical MERV13 use, eg 10 pascals or less delta pressure. Around 0.5m/s face velocity.
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Naomi Wu 机械妖姬
Naomi Wu 机械妖姬@RealSexyCyborg·
@PlasticFull The study showed low counts at 35 CFM through 1 SQF of filter material. A five-filter CR-Box is around 47 CFM through 1 SQF of material times 12.7SQF- per room. That seems worth looking at how low it still is.
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Stefan Stojanovic
Stefan Stojanovic@PlasticFull·
@eddericu @sri_srikrishna @ee_kelsey Stators good for boosting pressure, at expense of noise, narrowing outlet flow in pull config. Rule of thumb for boosting axials -bell mouth inlets -outlet stators -tubed outlet to media. or 2 in series Bigger media certainly helps. keep to EPA11 like QT3 or sqair.
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Stefan Stojanovic
Stefan Stojanovic@PlasticFull·
@RealSexyCyborg At what level of microplastics release should we be concerned? The ashrae study reported very low counts 👇 Without recirculation back through the filter. For context I end DIY smoke tests below 1 particle/cm3 due to resolution, below 1ug/m3 on a standard pm2.5 sensor.
Stefan Stojanovic tweet media
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Naomi Wu 机械妖姬
Naomi Wu 机械妖姬@RealSexyCyborg·
Throw me a bone here, like sort of a vague "yeah we should look into it some time". I've got HEPA filters all over the house and folks passionately advocating for no microplastic testing isn't super comforting😬
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Keşfet

@CleanAirStars @mishwoz @CleanAirClassrm @DouglasBooker @nathan_wood_8 @hugx4pets @BESAGroup @EllaRobertaFdn