ZERO Pro

I was gonna buy that but they said it may make noises high pitched, when in sleep mode etc. Ended up buying winix zero pro, not bad at all so far. Frankly I think that buying 2 good ones instead of 1 giant purifier might be better, small apartment or not. But im definitely not an expert so take my advice with a grain of salt. Im learning.

I live in Spain, so we may have similar products. I bought a Winix Zero Pro at a local retailer a couple of years ago and I'm happy with it. Dyson is generally overpriced. They have good products (we've had a couple of their vacuum cleaners), but they are often times too expensive nowadays. I can't say much since I don't know about purifiers, but stick to brands like Philips, Coway or Winix. Preferably avoid Amazon reseller "brands". And check for the prices of filters and how often you have to change them, you don't want to have to swap them every couple of months. Make sure to check reddit for comments on whatever you are planning to buy. Also, where are you planning to put it? If it's a big room, like the living room or a kitchen+living room kind of thing, you'll need a good one to be able to move all that air a bit, if you have several smaller rooms, you may be better off buying several of them but with slightly less power.

Just make sure buy a modern model. HEPA filters have evolved a bit over the years and so has the regulation. Old "HEPA" filters might not be true HEPA by today's standards. Just make sure you don't buy one with an ozone generator, or if you do, since many come with it (my Winix with PlasmaWave, for example), remember to deactivate it. They are not very good for people's health and I guess they are far worse for birds For reference, I have a Winix Zero Pro

No matter what you'll end up with, don't get a winix. Any of them. Baffled to see that, winix zero pro has been discounted (without a notice) and.. That on the EU branch, the filters aren't available to purchase anymore (out of stock). But worse, theirs hepa filters are not what they do claim to be, and they got a lawsuit. Such a bad experience. Never again.

Of those I'd go Winix, more so because I know Winix better than Phillips + Air Doctor, which are both decent brands I think too.  As well as Blue Air but that has ionizer that can't be turned off, so it creates a tiny (safe) level of ozone, but a small % of people will still have respiratory bother from even safe levels of ozone.   I think Air Doctors might have medical grade HEPA,.and more expensive filters.  So unless you were doing virus control, you wouldnt need to spend extra on medical grade just to filter pollen + allergens etc.(and HEPA still captures viruses, but the medical grade would just be better at it.) Phillips is probably good, but we don't really have much of that in US.  So id prob go with the Winix, as those perform very well, and it also has a ionizer but you can toggle it on/ off if you don't like it.  (The 'P" for Plasma button on the panel.)   I think that unit would give you about 5.9/6 air changes per hour with 4.8 being "good" and 6 being excellent..(rough estimate - not great with metric.)  So you would have very good to excellent air quality on high.   Edit: I would not get the Phillips because that is apparently a combo fan, and those are weaker units that move less air.  So that would only give you about 3.3 air changes an hour, which is a minimum of coverage, but not even "good".  Other normal Philips units, if big enough for your space, prob fine though. (Just not combo fan units.)

I second the 45i is a great unit, and they are sold at some hardware stores and such.  However I would also suggest getting the IQ AIr or Austin Air as well - as those are even better for VOCs - with many more pounds of carbon/charcoal pellets to absorb VOC gasses.  Alen will be the the best you can find at a store.  (They are good at both particulate and VOCs, but for VOcs you need to get it with their best filter, which is like 10-30 bucks more.). They also come with a lifetime warranty if you remain in the filter replacement program.  Although they don't move a huge amount of air so getting a Winix, Levoit, or Coway also a good idea to move more air/better/faster particulate capture.   The IQ Air and Austin Air also don't move a lot of air, so it's best to pair them with units that move a lot of air, so you get full coverage.  (Unless you could afford a lot of VOC minded units, but that is ofc very expensive.) So for me I have a mix of various brands with 2 Levoits, an Alen 45i, a Pure Enrichment Elite , RIA, and many others.  Some are good for VOCs, one has ionizer, and some are just strong for Hepa/participate coverage. In a basement id suggest a corsi Rosenthal box/CR Box.  As they don't look aesthetically pleasing....however for about 90 bucks....it will so about 400CFM power....which probably double the CFM power as all of those VOC type units do.  As VOC units move a bit slower....as that is better for the absorption of the gasses the charcoal/carbon pellets material.   Hepa-focused units will move air more quickly....so better for getting particulates and cleaning your air faster ..as they aren't focused in the VOC aspect (but can still help.). So I would definitely get at least an IQ Air or Austin Air for the VOC issue (they aren't in stores) a few Alens are down for general coverage+ effective at both, and then some stronger units for participate capture, which can be any of Winix, Levoit, or Coway.  All perform pretty similarly in tests of participate capture as the top 3 (with Dyson, which is overpriced for what it does but slightly quieter and with better sensors.).  But if you get a 30 dollar box fan and tape it to a set 4 merc 13+ filters...you get 400CFM power on high....which is as much or more than pretty much every consumer purifier under 400-500 bucks.  (And all the VOC units too.).  Lastly, ventilation for VOCs important as someone else said, so box fans great anyway.  Even putting a merv13+ filter behind a box fan...can help with CFM coverage and get you around 150Cfm...which is = to a 160 dollar air purifier about.    

Even if they dont work as well, they will still help clean your air. Maybe they do 98% instead of 99%, it will depend on the manufacturer, and lots of things. Its not a big difference. As long as you already have a solid unit, as you do with a Winix, then additional units for additional coverage arent as important on that stuff. It will still help. (and esp if the filters in question have good reviews, meaning they are likely fine.)

Why would you toss them if they are free ? (and working normally) Anything that helps with CFM is good. Those units are over-priced perhaps, and have various electronics issued ive read for those that paid money to buy them new. But for you - its free. Thats great. If it is in good working order, it can help clean your air. Germ Guardian isn't a great brand really, so they are probably better than them. If you only have 2 units, you likely need more, in order to get to excellent air coverage. (I have 8x units from various brands, in a large 1 bedroom apartment, although I have old smelly carpets I inherited here.) So as long as they work properly...I would absolutely keep them. (or give them away to someone that needs short of that.) But again with only 2 units you probably aren't getting more than 400 range CFM total, which is not enough for 6x air changes in a moderate sized space. You probably just have adequate coverage right now. So those might help get you to excellent coverage. Brand doesn't matter so much with HEPA. (If its HEPA it cleans 99.97% regardless of brand. Some brands might be off by fraction of a % in various scenarios but will still help you clean your air, even if its at 98% or whatever.) Brand stuff matters more on cost , special features, and aesthetic choices. Free units will absolutely still help you clean your air. Only catch might be if the filters are more expensive than new units or a box fan + merv 13+ filter. But you mentioned you can get filters for cheap (also usually fine if from a seller that has good ratings, as others have already tried it and liked it)....so you are good...enjoy your better air quality.....

Well I would definitely check the inside for any mold, as that would be the key worry.  As well some of them might use a PECO technology ?  So hopefully that doesn't have any visible light, or any/much ozone. (I have a unit with PECO that allowed the visible purple light to shine through the top, which hurt my eyes after looking at it a bit, but I don't think that brand does that.)  Although I think it might produce a tiny (safe) amount of ozone, perhaps.  As well make sure no ionizer that can't be turned off, but don't believe so.   Those would be the health aspects to consider.  So if they are otherwise clean and work fine...then yea...should be OK.  Only other caveat would be if they had some kind of of malfunction.  (Such as Aroeve units recently had a few units out of 50,000 or 100,000 catch on fire...and got recalled.). But I have not heard of any recall with Molekule.  Someone probably saw that they got sued and thought the units were bad.  (So marketing claims, which lots of units have gotten sued for various marketing claims, and apparently the air quality sensor on one unit can be off by a factor of 10 on VOCs ?).  So I wouldn't rely on any sensors it has.  But it will still help, just check the things I mentioned.   I will say buy good quality units when you get the funds and calculate your CFM needs, and when you eventually get enough good units for your needs then give them away at that time.  (So I'm not an expert in room sizes but if you put the dimensions of your space people can help calculate how much CFM you need.). In general a CR Box can cover 400-500 sq feet apparently and those do 400.range CFM.  So you would need 4-5 CR Boxes equivalent or something like 1,600-2,000 CFM total.  So even with all these Molekule units (that are just OK)...you will still prob need more....but they can help.  

I think the answer is both.  Although you can just put in a merv 15 or 16 filter yourself in the HVAC I believe, so you may not need to spend thousands of dollars there.   But the HVAC only runs at certain temperatures right ?  Vs air purifiers you can run them 24/7 all the time...for constant coverage.    That Lennox system seems cool, it's Merv 16 filters plus a PCO photocataltyic oxidation light purifier system.  Pco is in some purifiers too.  It can kill germs + converts VOCs into water vapor + carbon dioxide.  (VOCs are gasses essentially, stuff that creates odors, and sometimes even stuff we can't smell, that can still harm us.).  Idk what the data is on the light in that Lennox unit though.  Not an HVAC expert.  So idk if that's worth the money or not.  You can get PCO technology in purifiers such as PuraClenz, kaltech and others. Older  Uvc lights can produce ozone, but apparently newer PCO technology may not produce ozone.  One issue thigh, is that it might produce other unknown byproducts, when various chemical VOCs are converted.  So it's a new technology and IDK what possible compounds could occur.  I believe hfs generally considered safe thigh and I have two units.  (I use them sparingly and not daily like my other units.,) I would avoid the ion stuff as that will create at least a little ozone usually.  I am more comfortable with ionization in purifier units that I can easily toggle on/off.  So a larger unit like that might produce a concerning amount of ozone, idk, and it might or might not be easy to turn off.  But those would be things to consider there. The higher the merv generally good.  You want merv13+ I think esp for virus control.  So Merv 15 is very good.   I would avoid merv 11 as that might not capture certain viruses as well.   So it's a good idea to improve your HVAC, but you still want air purifier coverage for when the HVAC isn't running, I believe.  So you can get clean air with a lot of white hepa filter units they will capture virus particles.  Black carbon strips in fitness can Bind with smoke + help w smoke and odors.  Even better units for VOCs/odors will have like 10-15 pounds of carbon)charcoal pellets ..which absorb VOCs in the air.   You can try absorbing VOCs, or blasting them/covering them with PCO.  White hepa filters can't capture gasses so useless there.  But they are excellent at capturing partuculates, allergens, and viruses, if a good Hepa 13 filter I think.   So you have options.   But this a multiple approach as there are multiple needs.  I have 8x units in a large 2 bedroom apartment, each that does various things.  (One has ionizer, some are good for VOCs with carbon pellets, and some are just good for more HEPA coverage/particulate capture.).   I wasn't sure on safety with the PCO so I don't use those often, as that's a newer technology, and I test units before other people do.  If it were me, and I have the extra funds, I would consider the Lennox thing.  But can't say if I would get that or not.  As you can still get excellent air coverage just from people size + amount from air purifiers.   And you can buy yourself a merv 15 or 16 and prob put that in the HVAC yourself.  (Or have them but it's just a 150-180ish dollar filter, you don't NEED to spend all that money to have clean air.) But if you really want to be thorough....and you have the funds....and if you can toggle it on/off if there is an issue...then maybe consider that.  But you still prob need proper air purifier coverage too.   (I would avoid the ion stuff/merv 11 etc.)  Ionization fine in purifiers, for most, but can produce ozone and respiratory issue in some people.  So needs to be able to toggle on/off for first time user in my opinion.  Ionization can help particles bind together and fall to floor so you dont breathe them in as much.  It can help.  But you still then have particles on floor that need to be vacuumed up.  And some bothered by even small/safe amounts of ozone.  So id avoid In HVAC myself, but I do use daily in my main purifier unit.  White Hepa grade filters most important will capture particles, viruses etc.  That's the main thing.   Good units for VOCs/odors are 1,000 dollar IQ AIr and 750 dollar Austin Air.  Among others.  But those don't move a lot of air, slower better for the carbon pellets to absorb odors.  So best to pair with other units that move more air with HEPA. Lots of good brands there like Winnix, Levoit, and Coway, that all perform well, have various sizes, features etc.  

As others are saying...that's probably not going to do much.  As they have no listed CFM anywhere (as if they forgot to check the CFM amount ?). I would also not recommend rabbit air as your primary unit, as those do not move much air.  They can be OK for adding additional coverage, esp in a small room where space is an issue.  They also might be a little useful for VOCs, however since they don't move much air...they are not a good first choice for capturing allergens/particulates.  For that you need a lot of CFM power.  So a box fan tied to 4 filters...(Called a CR Box /Corsi Rosenthal box) Gets around 400 CFM power.  You need something like that with a lot of CFM power.  As well possibly mulitiple units depending how big the space.   So a rabbit air only does I think 113 CFM. It's very weak as it doesn't have much of a motor/fan.  It's has good esthetics and is OK if its like your 3rd or 4th unit to add to coverage maybe. But I would definitely not suggest that as your first unit that you are relying on to move + clean a lot of air.   (I would recommend it in a small bedroom, as a 2nd or 3rd if you already have a good purifier in there for general coverage.)  A 90 dollar CR boxfan purifier you make yourself will have about 4x more CFM power, therefore capturing 4x more particulates, and more quickly.  Thus way cleaner air.  Rabbit Airs do have some carbon in filters so can help with smoke/odors/VOCs, but again, powerful particulate capture...is not what's it's for.  So even a Levoit Vital 200 will do around 250 CFM I think, double a rabbit air for around the same price.  Winnix + Coway are also good brands.  List the dimensions of your space and I can give better idea what size units to get.  But CR boxes are the quickest way to get a lot of CFM power for cheap in the meantime.  That thing does look cool though, and if I was a museum I would want them behind every picture...as then you could maybe avoid a louder purifier.  But you might need 30 or 40 of those ...to have same effect as 1 strong air purifier with 400 CFM power.  (As they seem to not even have a fan ?, or very tiny if at all. As well a museum will hopefully have good HVAC system anyway.)  I also have an "art" unit I got for free that is made or sold by a prestigious musuem and can be hung on a wall.  Its a cool unit but decided not to hang it up as normal units are more powerful (and risk it might fall too). So you need strong units that will move a lot of air, or, a lot of units.  But those units you like aesthetically...are not going to do the job, alone.  You need much more.  (I have 8x purifiers in a large 1 bedroom apt. But I also have old smelly/mostly carpets I inherited here so my air is crisp + clean thanks to excellent coverage now.)    

Right, so I don't know your budget, but I believe a CR Box with 400ish CFM would give you around 5 air changes per hour...for borderline excellent air.  (4.8 is good, 6 is excellent.)  So you want to try to get I believe around 400 or even 500 CFM if you want excellent.   A 280 dollar Levoit Core 600 does 350 range I believe so that would be a good main unit.  And then a rabbit air with its 113 additional...would then have you in general In the excellent range.  So some combination like that.   However a CR box is only 90ish bucks as a box fan is 30 bucks and a set of filtrete 1900 filters are around 60 ish bucks.  You pay more for a traditional purifier, a namebrand etc.  And you pay even more for units that are more aesthetics minded like rabbit air and even more so the original unit in post.   So Winnix, Levoit, Coway all good brands.  If you have 1,000 dollars Dyson is fancy and quiet, although doesn't move much air for the 1,000 dollars.   So you can decide how you want to try to get to 400-500 CFM for excellent air, which units you want to get, but also keep in mind it's best to have 1 unit in each room.  So 1 in bedroom important too.  So a big unit in main room/living room, then 1 medium or small in bedroom etc.  (Can also have a 2nd nightstand unit or whatever needed to get to excellent.). So CR boxes the most affordable way to add lots of coverage.  You will pay high premiums for the units with aesthetics...per CFM value that you get.   But they can be fine in addition, and if you have the extra money to spend.   Also consider if VOCs/smoke an issue (then things like Austin Air is good, although 750, and they don't move a huge amount of air, and Alen is a good in-between, with decent CFM but also good for VOCs with their best filter.  And they come with a lifetime warranty if you remain in the filter replacement program.). They also look pretty modern to me, so I really like my Alen 45i.  I suspect you might like that brand, and that will move a lot more air than the rabbit Air.  (So that + a rabbit air might work.).  Another thing is ionizers and they are helpful but if you look at other units just make sure the ionizer can be toggled on/off.  In case it caused any respiratory issue.  Most units like Levoit or Alen don't have that.  Winnix + Coway have good units too, but some have ionizers so youd have to check closely.  But lots of units to pick from so depends on budget + what features you like.  (Some have air quality monitors also and other features etc.) 

I have a big purifier right next to my computer myself. (but not because of dust but more so because I have 8x purifiers in a 1 bedroom apartment so that happened to be the best spot for it.) So as others said you dont really need to put a purifier there, although it is more useufl to be near you. But also does not need to be. But next to a computer is an OK place, esp if you are using the computer a lot. But fine anywhere in the room thats gets good airflow. As per units Winix + Levoit are both excellent, however they are not known for being quiet per se. I find my Levoit quiet, and Winix scores about the same in decibel testing. However "quiet is subjective to the user, so you can always run them on low if needed. Thing is, if you run it on low you you are losing a bunch of the CFM effectiveness, so I suggest trying to run high and see if you adjust to minor noise. As CFM ratings are based on it running on high speed. (I got accustomed to the mild noise and now its a nice background noise....that I don't even notice.) Or at least run it on high when not in the room, or try to adjust over time, as you get more out of it the more/higher you run it. But certainly on low most units wont make much noise. My Levoits to me are not loud even on high. (Winix should be same.) I would not get a Xiaomi over Winix or Levoit, as I am not that familiar with Xiaomi, although those might be OK too. I do know that Winix + Levoit are both great. So either of those should be fine. Levoits dont have ionizer unless it says Plasma Pro. Some Winix I think might have it, but idk which models as I dont have Winix myself. (You also dont need ionization but if you get additional units you can always try out one of of those, just make sure you can toggle it on/off in case you dont like it.) But you should be fine with any Winix or Levoit.

I would not buy a Xiomi over a Winix unless there was a substantial price difference. (as in almost for free.) As I think it is a brand with less quality, so the units may break more frequently. As well they seem to discontinue units and then people can't find filters to even use them. Thus why they are cheap. The units I have had the most problems with...with units breaking within 6 months to 1 year...are cheap random brands. (they often usually only have a 1 year warranty.) I would strongly recommend Winnix or Levoit, as those are good quality, you wont be able to not find a filter etc. and they perform the best in recent testing. Here is a recent thread on people saying not to buy Xiaomi. [https://www.reddit.com/r/AirPurifiers/comments/1mgg0bo/do\_not\_buy\_xiaomi\_air\_purifiers/](https://www.reddit.com/r/AirPurifiers/comments/1mgg0bo/do_not_buy_xiaomi_air_purifiers/)

Cheapest + most effective is a CR Box/Corsi Rosenthal box.  So you buy a cheap box fan (30ish bucks) + a set of 4 filters (such as filtrete 1900 - around 60ish) so for under 100 bucks or so....you get a very powerful air purifier with around 400 CFM power.  Levoits are excellent and I still have two core 300s on the corners of my living room..m but 1 core 300 is not enough power. ( I now have 8 purifers for a 1 bedroom apt as I need excellent coverage since I have an old carpet I inherited here with 5x kids of mold on an test.). But my air is crisp and clean now thankfully.  So you aren't going to have excellent coverage with 1 90 dollar Core 300.  You might need 3-4 of them for excellent.  2-3 might be "good" coverage, perhaps. (Or just one of they larger units like the core 600 or Everest Air but those are around 350-390 I think)  Point is the Core 300s have 155CFM so great for a small or medium room.  For proper coverage, given allergies and such, you will need likely a lot more than that.  As general CADR numbers are based off 1 air change per hour I think. But you want 4x air changes per hour for excellent coverage.  (Every 15 mins.) So a CR box will give you around 400 CFM m, for 90ish bucks, about the same as a 350 dollar bigger Levoit unit.   So I would suggest tape together a set of filters to a box fan....while you save up if you want a bigger Levoit. But that is cheapest way to get very good coverage.  Prob 1 CR box + 1 core 300 in bedroom.  But keep adding units as needed.  Also this doesn't mention sound.  For more quiet units those are more expensive, like a 1,000 Dyson that doesn't even move much air.   Or you could get a bigger pricier unit and run it on low, to still get decent CFM.  But you won't get both high CFM, and very quiet, for the price point you mention.  Although I don't find box fans loud pet se, and my purifiers to me are quiet, all running on high.  I have gotten used to it and actually like the background noise and don't even notice it.   (As compared to when I got my first Levoit Core 300 and noticed it more.)  So you will probably just have to get used to the sound, as that can just happen naturally after a while.   But again, sound is subjective so idk exactly what is "loud" for you.   But fans are in purifiers and all fans make at least a little noise pretty much.  So it's a trade off but vastly worth it...for having better quality air.   Other good brands are Winix and Coway, also as loud/quiet (depending on ones opinion) as Levoits.  They all perform pretty close and top 3 in recent testing for both performance + decibels.   So a combination of 1 CR box + 1 affordable unit will probably get you a decent amount of base coverage.  Then add another unit/upgrade from CR Box later if needed.  (You can also still keep using the CR Box for even better coverage or even putting 1 filter behind a box fan when upright normally...can also add to coverage and save  space.) 

I missed the last part of your post about considering a 350 range unit at top end.  So the Core 600 is I think 269 on levoit.com or around 300 maybe on amazon. So I would get the best unit you can afford...and then add a CR box/other unit when you can afford another. I am not a expert in dimensions, but using the calculator on the wiki page w 1,000 feet and 8 foot ceilings, and a target goal of 4 ach (air exchanges per hour) gives I think 466 CFM needed. Now they page actually shows 4 air changes per hour on the cusp between "minimum" (3-4ach) and "good" (4-5 ach)  and it says excellent is actually 6 ach.  (You would need 733CFM for that.) So the Levoit core 600 gives like 391-430 depending on dust/smoke/dander etc.  So you would be at at least adequate protection....with just a core 600, and on the cusp of "good".  So basically in your living room, best the unit, you will have very good protection. And in a bedroom or further away room still adequate.  So that would likely be a very good unit to get to start.  And whether you want to add a CR box or a smaller purifier in bedroom for more coverage later...you can find out.  (The Core 600 + CR box gets you to 800 range CFM units running on high, so that gets you excellent. Core 600+ a core 300 in bedroom gets you almost 600 CFM, so very good coverage that way too.) Remember, a bigger unit you can lower/more units run lower, will be quieter but get you equal CFM.  So the larger unit is the best way to go by all accounts.  And just add another later if you want/need excellent etc. 

Yes, I am aware and as per Google (via IQAIr source + others)  "Yes, ozone produced by air purifiers can be harmful even at levels considered "safe" or compliant with regulations. Ozone is a toxic, reactive gas that irritates the lungs and respiratory system, causing coughing, chest pain, and worsening conditions like asthma, regardless of whether it is generated intentionally or by ionizers.  U.S. Environmental Protection Agency (.gov) U.S. Environmental Protection Agency (.gov)  +3 Why Ozone is Harmful Even at "Safe" Levels: No Truly Safe Level: Studies indicate that even small increases in ozone can cause significant respiratory discomfort, decreased lung function, and increased mortality, especially for sensitive groups like children, the elderly, and those with respiratory diseases." So yes the number is low, but it is not 0.  What is safe for "most" is not safe for every individual (and animal).  For instance I had a medical issue that is 1 in 4,000.  So even if 95% are fine...5% may not be.  (Or even 1 in a 1,000.). So why take the chance if someone has never owned an ionizing unit before ?  The bare minimum for a first time unit...is to at least have an on/off ability which blue air just does not have.  It might be a fine choice for even most people, but it won't be a good choice for everyone.  It's a risk for a first timer as they just wont know how they react to it.  As well consider that people might have multiple units running....and these tests are only done on 1 unit.  So if you have like 3,4,5 units all employing even a "safe" level of ozone...then you may be then getting above a safe level at that point.  As you will then be getting 3,4,5x as much ozone dose if you have multiple units running. It. As well the size of space also matters, as in one study they put a unit in a small bathroom...a unit which has the "safe" ozone levels under 50ppm or whichever metric...and even that created over the threshold to an unsafe level and what would be a level 2 safety smog alert.  (Not how the unit is intended to be used they acknowledge, but undoubtedly some people will be running too big or too many units ..and getting to possibly unsafe levels..even if each unit individually is tested "safe".) As well some say that no amount of ozone indoors is safe to breathe. (As IQAir seems to be saying and that "safe" level keeps going down further and further...so we really don't know what is truly safe, and certainly safe for most...is not safe for every person.). Especially for their first unit.  It's just a flaw with BlueAir even if their units are good quality.   "Underwriters Laboratory’s UL Standard 867 requires household air purifiers to produce no more than 50 parts per billion (ppb) of ozone. However, even this level is not safe for humans to breathe." https://www.iqair.com/newsroom/are-you-polluting-your-home-ozone Note: I use a different brand one with ionizer, but I toggle it off sometimes. I like the function, so that works for me. But for a first time buyer...it must have toggle on/off otherwise it's a risk that they may not like the unit, or maybe even detrimental to thier health/animals etc.  

Sharks don't perform that well for what you pay, and their filter thing is kindof a gimmick. (The small print says when running at half speed 12 hours a day I think.  Well of course the filter will last longer if you turn it off 12 hours a day....). They don't perform that well in testing, just OK, and are beaten by more affordable units in performance.  Which you can see in this video.  (Around 20:54 he shows the screen with all the data and says the winners.) https://youtu.be/sQGfO4hNb60?si=4lONOYdNRzZ-hAe7 (In the test they tested a 250 shark model but the one you are talking about I see as like 140 ? So their even more powerful/expensive unit....even got beat by a 90 dollar Levoit Core 300 + other brands.).  So your smaller one will be even weaker of course.  In terms of sound it's hard to say, but decibels on Max Winnix to the shark not too different at 54 to 63, just slight difference.  As the Shark a little quieter as its weaker too.  And if you will be running it on low or medium when asleep turn just get the more powerful unit which will move more air on quiet mode.    As well you might come to like the sound of the purifier, as I like the sounds of mine, as background noise which I don't even notice anymore, like a sound machine (which I also have so even on high my purifers aren't louder than the sound machine,as about the same)  so that actually helps me sleep.  So I used to be concerned about the sound when I got my first unit...but then I got used to it.  And now I run them on high always and I don't even notice it.  So you very well might become used to the sound.  So you should get the better unit,and start off running it on low or medium, (of sound and issue) which is pretty quiet, and will filter more air.  (Otherwise run on high for the listed CFM measurements.  As running it In low gets you like 33% of the listed CFM power.  Medium. Maybe 50% range CFM power.  So you loseca lot of CFM power just by running them on low or medium.  Best performance on high.  But caveat is running a 2x stronger/bigger unit at 50% speed still filters as much air as a 50% sized unit going max.  And will often be quitier that way too.). So again, you might come to like the sound, and you can always lower the sound by playing with the 3 settings if needed, so I wouldnt get the weaker shark...even if it's slightly quieter.   Winnix was #1 on the tests and I would get the Winnix. (I've never had sqair so I am not familiar with that one/can't say much on that.)   Also I haven't done the math to know if those are good unit sizes for your space. But Winnix has various sizes, so of those 3...id get a Winnix of whatever appropriate size. 

The "not Hepa" thing is really not that important, and I think some technicality.  As Levoits still do an excellent job filtering the air.  It just might take a few seconds longer or some such.  As even running it on different speeds can sometimes determine if it's officially that threshold or not.  If it's like 99.7% close to the threshold on some setting, it's really not important.  As multiple brand have all been sued for the same thing, including Winix and Alen two other very good brands (as well as Coway same issue on some speed settings apparently  + many more brands.).  Levoits out-perform many other units in testing, which can be seen here.  As the guy even picked the Levoits as the best-performing units for their size.  At around 20:54 he shows the chart with the results...top brands were Winix, Coway, and Levoit.  Winix + Levoit have both been sued by some California consumer affairs on the same technicality. It is ultimately unimportant...if they are pretty much at the threshold,  but dip below it by a fraction of a % on whatever testing they did.  (Which is seemingly not revealed.).  Someone said they think no consumer air purifier is true hepa as it's an issue with marketing in the industry, more so than performance, if even the top units are having an issue on the technicality.   As again...when testing...both Winix + Levoit perform exceptionally...beating all other units in performance.  (With Coway + Dyson, Coway has an issue with anti-bacterial coating on its filters and Dyson is over-priced for its performance and apparently is the one that made the claim against Levoit....and they found the Levoits actually filter more air per dollar cost than the Dysons so. (So HEPA 13 but moving the air more slowly...actually removes less particulates. Vs hepa 12.9 essentially...but faster/more powerful...performs better in removing particulates.) The levoits do also score "high" on sound on high ( I don't find medium sized or smaller air purifiers loud myself.). But...it's the same with Coway + Winix.  All the top 3 performers were the "loudest"...as moving air quickly makes noise.  A Dyson is very quiet.  You might like that. However it is vastly over-priced and doesn't move much air for the price.  As well I believe it does nothing for smoke or odors.  (Or perhaps it has a small amount of carbon in filter, I am not sure, but Levoit has that too.) So Coway is actually even louder than the Levoit + Winix tested,  although all in the same range.  Coway will definitely not be any quieter though. They also have an antibacterial coating on their filters...which is technically a fungicide/pesticide...but at like 0.000071 on medium.  But apparently it wasn't even tested on high.  So it's a concern for some people.  So I would absolutely not get rid of a good Levoit unit just because the HEPA thing, and Coways are just as loud and even slightly louder as you can see on the decibels chart in the video. Winix about same too.).    What you can do is get more units, and run them on low.   Alen is also a quiet brand, but a little pricier.  Alens also have carbon in filter with their best filter, and come with a lifetime warranty.  Their smallest unit, a 25i might be good for a bedroom as well. ( I love my 45i but not sure of the dimensions exactly of the smaller 25i.) But I would keep the Levoit and just run it on low.  Or move to another room where sound less of an issue for you, as they are still very good units. (Again performing in the top 3 with Winix + Coway, same with sound all are about the same in sound, no material difference there.)  The HEPA thing is more a marketing issue than performance.  Levoits are amazing units....that last a long time....(I've had two core 300s running near continuously for 5+6 years now...)  But look into Alen 25i and/or run two units on low.  But Coway won't be quieter or perform vastly better than Levoit. As all 3 of the top brands tested recently all perform pretty close to each other...in multiple areas.   At about 20:54 of this video shows the chart with the results.  https://youtu.be/sQGfO4hNb60?si=UTlmfH9mpKDrgxEj

Blue air has (safe/low levels) of ozone but you can never toggle it off on thier units. Winix usually has an ionizer that can be toggled on/off, although I think it reverts back to "on" every time you turn it on/off.  Coway some have ionizers, but make sure that it either doesn't or can toggle on/off.  (I think the 350 doesn't ?, and looks like a good unit.) You could also consider a Levoit Core 600, as you don't need true Hepa for excellent particulate removal, and Levoit is true Hepa on low/sleep mode, and not on medium/high, same as Winix and Coway, they all have the same issue...and all perform really well.  (HEPA 12 is 99.5% which is still excellent, so the difference between 99.5 and 99.7...is a few dozen particles out of 10,000.).  Levoits are excellent at cleaning the air, but you already said you like that Coway 350, so I would say just get that.  If choice is  Coway 250 or Levoit Core 600, I would get the Levoit.  (Bigger/Better coverage at that point.)    But the Coway 350 seems like a great unit, so if you can afford it, I'd go with that.  (The Coway 350 and 250 are essentially the same I believe, one is just bigger/better coverage.)  Edit: you said you have 620 sq feet but is that for say a living room, or your whole space ?  As the Coway 350 has 2640 feet of coverage. Meaning you would only be getting about 4.3 ACH, air changes per hour.  Wheras the Levoit Core 600 is 3,000.  Meaning that would give you about 5 ACH, where 4.8 is "good" and 6+ is excellent.  However if you mean your whole space is 620 and your living room or whatever is maybe 400sq feet then you would be fine and be at good to excellent with the Coway 350. 

Good brands are Winix, Levoit, and Coway.  Levoits give a great value and I often suggest for first time buyers as they are simple, but very effective. (If you want an ionizer for example Winix has that, with toggle on/off, but I would not suggest that for a small dorm room with likely poor ventilation, as they give off a little (safe level) of ozone.  But even a safe level of ozone can bother some people, and in a small space with no ventilation the ozone level can increase to a problematic amount sometimes too.  So I would avoid ionizer, and all Levoits have no ionizer by default. Some Coways I think might not have ionizer, but you would have to check. (Levoits only on the "plasma pro" line, all others by default do not have ionizer.) So something like a Levoit Vital 200s would be a good choice for you.  As well as a fan near a window, to push fresh air in (point fan inwards, as it will draw fresh outside air into the back, and push that fresh air into your room.  - Edit: nevermind if you have seasonal allergies.) Another budget friendly option is something called a Corsi Rosenthal Box/CR Box, which is simply 4 merv13+  filters (such as filtrete 1900) .....taped around a 30 dollar box fan.  This gives a whopping 400 range CFM, more than most 400 dollar purifers.  Although it is a bit bulky and less aesthetic.  So I would suggest a Levoit Vital 200s + a box fan, which will cost you about 190ish. (If you dont already have a fan.  As well you can add to CFM coverage by simply putting a merv filter behind a fan...as that will collect particles and help clean your air.  A merv 13 filter behind a box fan can get you around 100-150 CFM, about the same as a 120 dollar range air purifier.  (For less than half the cost.) But normal purifiers are good too, as they can save space, have the filter replacement warning, and air quality monitor on some.  So get a normal unit as you can afford it, but if you still need more coverage...then add fans/filters and/or make a CR Box if you need more coverage. (I have 8x units in a large 1 bedroom apartment, an old smelly carpet I inherited here with mold etc. My air is crisp + clean now so no more symptoms..).  A Levoit Vital 200 at 1,800 feet of coverage will get you excellent air coverage at about 13ach on high. (Air changes per hour.). 6 is excellent.  I get 8-11ach depending on how high I run my units.  So at 13ach you will probably...be pretty happy with what.  And you can run it on medium for more quiet and still get excellent, and low mode for even more quiet would still get around 4.8ach etc.  So various benefits to getting the bigger size, but mainly - you want those symptoms to stop - so get the best you can afford + the most CFM coverage.  So that's 250CFM power for only 160 bucks with the Vital 200s.  (Run it on high mostly to get the benefit, as all CFM numbers are based on the unit running on high, running on low only gets you like 1/3 the listed CFM coverage.)

Get the Levoit Core 600, its on sale on amazon for 250 right now. It has 390 CFM power, the Core 300 only has 145. Meaning its more than twice as powerful. That would give you excellent air quality, with almost 8 air changes per hour (what I have, and I had to get excellent coverage as I had bad allergies as well, and an old smelly carpet etc.) 6 Air changes (ACH) is excellent, 4 or 4.8 is good. The Core 300 is a great unit although that is rated for 1,073 feet. Meaning it would give you about 2.5 air changes per hour in 400 sq. feet. Which is just a minimum of coverage, and not even "good". so for those with allergies and/or bad air conditions...you will likely want excellent. Which is more like 2,000 or 3,000 feet of coverage, so bigger units than what you are looking at. But you dont need an expensive woozoo fan imo. Just get a better purifier. You can get a 30 dollar box fan which will move more air than the woozoo. You can also even tape merv 13+ filters around a box fan...and create a DIY purifier that does 400range CFM power. Lastly, you can even put 1 merv 13 filter in front of/behind a powerful (but cheap) box fan...and get around 150 CFM, or about the same CFM power as the purifiers you are looking at. So get a Levoit Core 600 + a box fan if you want. (if you want ionizer you can also get a 600 plasma pro for 50 bucks more I think,but you dont need ionizer.) Main thing is Hepa with most CFM power, that is what will capture particulates. Ionizer is a nice to have, I use one on one of my 8 units, but not at all neccessity. (You could also add the core 300 with ionizer or other inoizing unit later. right now...id suggest the Core 600. (They also have some carbon pellets in filters, to help with smoke/odors, and the bigger unit will have more of that.) Although the best units for VOCS/odors are very expensive like 750 for Austin Air or 1,000 for IQ Air. Alen also decent but not nearly as good as Austin Air/IQ Air, but would be a litlte better for VOC's. But again...meain thing is CFM power for capturing particulates. For ktichen smells thats where the fan comes in + use hood range, + bathroom exhaust fan, open windows etc. to ventilate. A Levoit will help a little on that but ventilation key there. And the Levoit 600 will be excellent for your allergies and getting rid of particulates. The Core 300 and the other units you are looking at aren't large enough to get you excellent air quality. (just minimum coverage, which is often not enough for those of us with allergies.) Winix also has good units at the slightly higher price point that would provide the adeqaute size. I would avoid blue air as you cannot toggle the ionizer of on those. (in case you have issue with it, as some people get respiratory disrress, sortof how hiking at elevation makes some people want to cough...despite the air also being more clean. Everyone will have a different threshold on that, so best if you can toggle on/off esp for first time buyer imo.) Sharks are not as good as those other brands, and just OK. (The Levoit Core 300 beat the Shark in recent testing, depsite the Shark costing more, they have a sortof "never replace the filter" schtick (or whatever it is), but they dont clean the air as well as the better units like Winix, Levoit, and Coway.

IQ Air is one of the best as the Health Pro Plus Xe I think does a good 300ish CFM while also having I think 15 pounds carbon pellets + related to absorb odors/VOCs/smoke etc. Although if your allergies are purely particulate based you can get 400CFM of particulate coverage for like 90 bucks with a DIY CR box /Corsi Rosnethal box.  (A 30 dollar box fan taped to a set of 4 merv 13+ filters is as much or more particulate coverage than you will get from any 300-400 dollar air purifier pretty much.)  So you don't need to spend 1,000 dollars on a unit to get good air.  If smoke/odors/gasses and allergies related to those issues then definitely IQ Air.  And it's one of the best units anyway.   But for physical allergens many units do very well, units from Winix, Levoit and Coway all perform really well and close to each other.  In particulate coverage.  So I like Levoit as they are simple and effective and good value for what you get.  So a Levoit core 600 is a powerful unit with 390 or so CFM for 280 bucks or so.  Has air quality monitor as well.  If you want an ionizer you can get the plasma pro version, but be careful as ionizers can cause respiratory distress in some.  So some Winix + Coway units have ionizer that can be toggled on/off but you have to look closely.  As well Coway uses an antibacterial fungicide on their filters in low/safe levels but if you have allergies relating to that then I'd go Levoit or Winix,  but they are also good units otherwise. Dyson are known for being very quiet and have good air sensors but they don't move much air.  I think it moves as much as the Levoit 200 you already have...but it costs like 800 dollars more.  So not really worth the cost if you just want the best particulate coverage.  Alen is a good brand too that is kind of good at both particulate and VOCs, with their best filter.  And they have a lifetime warranty if you stay in filter replacement program.  Austin Air are also 2nd best for VOCs,  but don't move much air in terms of particulate coverage.  I think it's a good idea to have a unit good vs VOCs even if it's not your top priority so maybe an Alen 45i or 75i + a Levoit Core 600 or similar priced Winix.  Alens are also quieter, but don't move as much air as Levoit/Winix/Coway.  As slowly air flow is better at absorbing VOCs/gasses with the carbon pellets.  Levoit has some in their filters but not nearly as much as those other units more tailored for VOCs, so a Levoit can still help a little in that regard likewise Winix + Coway also I think.  But Alens are a little better for VOCs a little quieter and a little slower, but still decent at CFM speed.  IQ AIr best units also good at both and better than the Alen by a lot.  Austin Air very good VOC, kinda slow for particulates.   So again, depends what types.of allergies/needs.  But for just particulates, with a little help on VOCs...Levoit, Winix, Coway all pretty great.  Or even a CR Box which at 90 bucks and 400 CFM rivals or outdoes must about any unit for particulate coverage.  Even 1 box fan with a merv 13 filter in front/behind it..can do about 150 CFM...pretty close to what the vital 200 does.  As box fans are big,.cheap, energy efficient...and move a lot of air.  That's essentially all most purifiers are.  A filter + a smallish fan to move the air around.  You pay more for air quality sensors, filter replacement reminders, apps and various others features.    But lots of units can capture particulates every well,.even 90 dollar CR Boxes + related.  So something like a Levoit Core 600/Levoit Everest Air/Winix + a unit for VOCs like Alen might make sense.  (Alens are sortof thin so a hallway might work.)  Or get the IQ AIR if you have the money to spend.. but you will still want another unit too for total CFM coverage.  Lots of options...so what features are most important to you ?    Another really thin unit is Rabbit Air, as you can even hang them on a wall...however they also don't move much air.  Maybe if you put two, on one each wall, but that's pricey as they are a bit Dyson-esque in paying like 250 bucks or so for only I think 113CFM. So two of them would be around 500 bucks for only 226 CFM...so definitely not good value.  But space wise can be useful in some instances perhaps.  

I got one from Winix zero x air purifier. Go from the square meter coverage, and one with a hepa filter. What are your priorities, budget, does it have to be quiet/small etc?