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Old 25-04-2019, 07:33 PM   #2851
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Thank you very much for your detailed reply, this information is very useful. It makes sense there is a risk of the transformer malfunctioning, I think I will now probably abandon the idea of buying a 120V AP.

I am an expat living in Hong Kong, unfortunately my Chinese language ability is not that great so it can be difficult to understand Chinese reviews.

You are correct that Xiaomi 2S is available in HK retail, it is widely available locally for HKD $1,099 (approx. USD $140) which is obviously very cheap. Today I went to an electronics store to look at the Xiaomi 2S, I am happy with the price but have some concerns about the quality. Specifically, I am concerned about the quality of the HEPA filters, are they on a par with leading international brands such as Coway / Philips?

One other final option I am considering is buying the Blueair Blue Pure 221 from Germany. Since Germany uses the same Voltage/Frequency as HK/SG, there is no need to use a transformer. I have found an online retailer in Germany which sells this AP for EUR 316. They can deliver directly to HK for just EUR 35, so the total cost + delivery would be EUR 351, which is approx. USD $390.

From my research it seems the Blueair Blue Pure 221 is basically the 230V version of the Blueair Blue Pure 211, which is the highest ranked air purifier amongst all 36 reviewed and tested by US website Consumer Reports. Has anyone here ever used this AP?

Any thoughts on whether I should go for the Xiaomi or the Blueair?

Just go for the Xiaomi. All these filters can do 0.3 microns no issue.
The CADR (Clean Air Delivery Rate) of the Xiaomi 2S and Pro are 310 m3/hr and 500 m3/hr respectively. That is the spec to look out for, and after that would be things like noise level and then power consumption.

The 2S and Pro are pretty ok after you dial down the speed in the app control, just that in max fan speed mode they are very loud, louder than other APs in max fan speed mode. However the thing is that these APs are pretty small in size, so if you are talking about device volume : noise ration, the performance is still decent. And also due to the its taller stance and small foot print, it makes sense in a small apartment in Singapore or HK.

There is a small -ve of the Xiaomi 2S and Pro, actually any Xiaomi air purifier. Their Auto fan mode doesn't really work, coz they set the higher fan speed to kick in at too high a PM2.5 ug/m3 concentration level.
It's a quirk of the AP, can't be helped. Seriously, quite a few other APs also are of this nature, so isn't a big deal.
Most of us just use manual speed, really not a biggie in real life usage.

Forget about the Blueair. The filters are extremely expensive.
The Blueair 221 has a CADR of 590 m3/hr, so it'd be like a Xiaomi Pro competitor. The good thing about the 221 is that it is relatively less noisy than the Pro (56 dBA for the 221 vs 69dBA for the Xiaomi Pro, which is bloody loud).

The Blueair 221 is 33 x 33cm x 52cm. Xiaomi Pro is 26 x 26 x 73cm.


There is another point called the Formaldehyde CADR, that is another point to consider for other pax having this specific need due to other reasons (basically VOC pollution and protection, touched before in the past 5 pages due to a very specific case that happened in Singapore).
But pls if anyone is having some formaldehyde outgassing issue, the correct way to treat it is not to have big ass APs with really high formaldehyde CADR (eg the X352 X83C Plus) but you'd need to get the temperature of the room to relatively high levels to speed up the outgassing.
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Old 25-04-2019, 07:37 PM   #2852
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Get 2 Xiaomi Pros if you feel like it, it'd give you 1000m3/hr CADR capability if the situation really needs it, but when they are throttled back, the noise levels shd be slightly lower than the Blueair 221 pumping the same amt of airflow. Basically then you'd be covered for 2 rooms, or you can use 2 x APs in a single room eg master bedroom).

And still you'd save on the filter and cost of 2 APs still ought to be cheaper than USD 390.

Do more shopping, am sure you can get cheaper prices on HK online sites.
Get in touch with your HK colleagues, xiaomi is a very ubiquitous brand over there. Everybody knows where to get the best price. HKers are extremely price sensitive like us Singaporeans.

eg In Singapore, we get our Xiaomi 2S at only USD 100 thereabouts. No way HK is going to be that much more than SG.
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Old 25-04-2019, 07:40 PM   #2853
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Blueair 221 - 33 x 33 cm = 1089 cm2 footprint.

Xiaomi Pro - 26 x 26 = 676 cm2 footprint. 2cps = 1352 cm2 foot print (no worries, can site them 2pcs side by side). But of coz, visually the Xiaomi Pro would be 73 cm tall, even though you won't be able to make use of that vertical space in real life be it the Pro or the 221.
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Old 26-04-2019, 06:23 AM   #2854
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Today I went to an electronics store to look at the Xiaomi 2S, I am happy with the price but have some concerns about the quality. Specifically, I am concerned about the quality of the HEPA filters, are they on a par with leading international brands such as Coway / Philips?

BTW, the CADR values of the Xiaomi has been verified before by 3rd party labs.

eg This is for the original ver 1 xiaomi. Published spec = 406 m3/hr

Tested 396 m3/hr




Actually Xiaomi has another bigger version called the Xiaomi Max, it has a CADR value of 1000 m3/hr. It's 2X the price of the Pro, but i reckon it's a bit less flexible in usage than having 2 pcs of Xiaomi Pro.
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Old 26-04-2019, 09:43 PM   #2855
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BTW, the CADR values of the Xiaomi has been verified before by 3rd party labs.

eg This is for the original ver 1 xiaomi. Published spec = 406 m3/hr

Tested 396 m3/hr




Actually Xiaomi has another bigger version called the Xiaomi Max, it has a CADR value of 1000 m3/hr. It's 2X the price of the Pro, but i reckon it's a bit less flexible in usage than having 2 pcs of Xiaomi Pro.
Thank you again for your kind and informative reply, this has helped me a lot. Since this is my first time to ever buy an AP, I would probably start by just buying one Xiaomi 2S (my apartment here in HK is extremely small, total size of entire apartment is only approx. 25 m2.)

You are correct that you can get cheaper prices on HK online sites. There is a popular shopping comparison website price.com.hk The price of HKD $1,099 is for the “official” Hong Kong stock. Another option would be to buy a parallel import (水货), which sells for approx. HKD $800.

Today I have been doing some more research about the Xiaomi 2S, there are two points I am concerned about:

1) During the video 「FView 出品」空气净化器横评(测试篇)the guy states that for Xiaomi it is NOT possible to separate the outer layer primary filter (used for filtering out dust, hair and large particles.) from the inner HEPA filters. Therefore, the only way to remove dust from the outer filter is by scrubbing it off.

I am concerned about this because I believe it is better to be able to remove the outer layer primary filter and wash with water to remove all the dust? I saw on reviews of other APs (such as Coway and Bluair) that users remove the outer filters and wash them with water.

2) I saw a website [ smartairfilters.com/en/blog/xiaomi-auto-mode-leaves-air-unsafe-86-hours/ ] which claims that for Xiaomi AP it is only possible to use manual speed for 3 hours, and that after 3 hours the AP will automatically go back to Auto mode. However there are also some comments there is a “workaround” to fix this, so maybe this isn’t an issue?
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Old 27-04-2019, 09:12 AM   #2856
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All my 5 x Xiaomi Pros do not auto trigger back to auto mode. I have been switching on throughout the night. Running under manual mode. Overnight.

But I not blasting at highest speed. Maybe very high / highest speed will? I not sure. Didn’t try. Too noisy. My comfort zone (for Hall AP) is running the manual speed @ coverage 23-40m2 selection. Didn’t auto trigger back. No issue.

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Old 27-04-2019, 10:46 AM   #2857
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Before I switched from other brands to Xiaomi, I also have qualms about the filter. Especially when you compare those that have relatively much thicker HEPA filter than Xiaomi.

I have used several brands before I changed all to Xiaomi. Not that they no good. They are good. But original filters are getting expensive. I just need something that able to bring down the PM2.5 fast and yet, low maintenance cost. And I was looking at mobile app operating that time also. All purifiers have their own pros and additional functions. Some more features. Some lesser. If looking for something that emits negative ions, then Xiaomi AP is out of the picture.

I used a stand-alone PM2.5 device to check the air “quality” from the outlet. Xiaomi or non Xiaomi, clean air coming out - in terms of PM2.5 readings. Able to achieve what I’m looking for.

As for filters “lasting” (Xiaomi and non Xiaomi AP that I have used before), all have tint smell as time goes by. (At least for my usage/ environment/ situation/ at that time) Maybe some faster. Some slower. Depends on situation. Since Xiaomi filters are relatively cheaper, I just change them when the filter lifespan reaches around 30%. I usually don’t wait until 0% (individual preference). I no longer bother about vacuuming or clean or whether able to wash prefilter, this and that.

Choose a purifier that one feels most comfortable with it. There’s no “best” purifier imo. All got their own pros and cons. Depends on individual.

Last edited by Lucky177; 27-04-2019 at 11:10 AM..
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Old 27-04-2019, 11:30 AM   #2858
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Thank you again for your kind and informative reply, this has helped me a lot. Since this is my first time to ever buy an AP, I would probably start by just buying one Xiaomi 2S (my apartment here in HK is extremely small, total size of entire apartment is only approx. 25 m2.)

You are correct that you can get cheaper prices on HK online sites. There is a popular shopping comparison website price.com.hk The price of HKD $1,099 is for the “official” Hong Kong stock. Another option would be to buy a parallel import (水货), which sells for approx. HKD $800.

Today I have been doing some more research about the Xiaomi 2S, there are two points I am concerned about:

1) During the video 「FView 出品」空气净化器横评(测试篇)the guy states that for Xiaomi it is NOT possible to separate the outer layer primary filter (used for filtering out dust, hair and large particles.) from the inner HEPA filters. Therefore, the only way to remove dust from the outer filter is by scrubbing it off.

I am concerned about this because I believe it is better to be able to remove the outer layer primary filter and wash with water to remove all the dust? I saw on reviews of other APs (such as Coway and Bluair) that users remove the outer filters and wash them with water.


2) I saw a website [ smartairfilters.com/en/blog/xiaomi-auto-mode-leaves-air-unsafe-86-hours/ ] which claims that for Xiaomi AP it is only possible to use manual speed for 3 hours, and that after 3 hours the AP will automatically go back to Auto mode. However there are also some comments there is a “workaround” to fix this, so maybe this isn’t an issue?
(1) The prefilter can be cleaned by vacuuming. I am sure you have cleaned your aircon prefilters with vacuum before. Very little difference vs washing, in the context of the air purifier.
I have a Mfresh M8088A that has a filter construction that is the same as the Xiaomi (ie cylindrical filter with prefilter built into the cylindrical filter, just that the Mfresh is a bigger filter. I also vacuum my Sharp and Samsung AP prefilters, though sometimes i do wash that.



(2) Yes, if that ever happens, just set timed programs. Seems like Lucky177 does not get it with his XM Pro.

https://forum.thaivisa.com/topic/108...mment-13816765

Second is the Manual Mode if set above ~50% fan speed will revert to Auto Mode after 3 hour - basically shutting itself off... My guess this is to reduce motor wear and filter usage...

But you can easily work around this problem by setting up a timer setting to reset the unit prevent the 3 hour mode change from Manual to Auto... Just add automation rules that turns the unit off & on every 2.5 hours and the purifier will stay in manual mode for the whole programmed time...

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Old 27-04-2019, 08:29 PM   #2859
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(1) The prefilter can be cleaned by vacuuming. I am sure you have cleaned your aircon prefilters with vacuum before. Very little difference vs washing, in the context of the air purifier.
I have a Mfresh M8088A that has a filter construction that is the same as the Xiaomi (ie cylindrical filter with prefilter built into the cylindrical filter, just that the Mfresh is a bigger filter. I also vacuum my Sharp and Samsung AP prefilters, though sometimes i do wash that.

Hey WussRedXLi and Lucky177, thank you both for your replies! That’s all my questions about AP now answered, my conclusion is that I will start by buying one Xiaomi, then add more later if necessary.

On a separate topic, I have also decided to buy an Air Quality Monitor (to keep track of the quality of air in the apartment BEFORE and AFTER using the new AP, so I can make a solid judgement on the AP's performance)

From the research I have done online it seems that the Laser Egg 2 Air Pollution Monitor might be a good choice? (It costs RMB ¥599.00, which is approx USD $90)

Would you recommend this one, or are there any alternative Air Quality Monitors you would recommend instead?

Last edited by ChanOwen; 27-04-2019 at 08:46 PM..
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Old 28-04-2019, 01:07 PM   #2860
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Hey WussRedXLi and Lucky177, thank you both for your replies! That’s all my questions about AP now answered, my conclusion is that I will start by buying one Xiaomi, then add more later if necessary.

On a separate topic, I have also decided to buy an Air Quality Monitor (to keep track of the quality of air in the apartment BEFORE and AFTER using the new AP, so I can make a solid judgement on the AP's performance)

From the research I have done online it seems that the Laser Egg 2 Air Pollution Monitor might be a good choice? (It costs RMB ¥599.00, which is approx USD $90)

Would you recommend this one, or are there any alternative Air Quality Monitors you would recommend instead?

Just get one of those USD 30-40 laser particle counter type of meters would do. All are around the same. Don't need internal battery/portability as well, since it's very likely that you'd be plugging into a power bank, which would give you a good 12-24hrs worth of operation. They are many on Taobao, am sure you can find on HK's online sites as well.
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Old 03-05-2019, 01:16 PM   #2861
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hey guys, there is a lot to read here. I'm thinking of getting an AP but not sure if it's worth the investment. Currently NEA PM2.5 reading is 17, how clean can each of the various AP models bring down from this number? (according to laser measurement and not AP's inaccurate reading. There seems to be lack of test done on each AP with laser readers)

Is single digit PM2.5 possible?

Can you really smell/feel the difference in air quality at single digit?
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Old 03-05-2019, 01:43 PM   #2862
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hey guys, there is a lot to read here. I'm thinking of getting an AP but not sure if it's worth the investment. Currently NEA PM2.5 reading is 17, how clean can each of the various AP models bring down from this number? (according to laser measurement and not AP's inaccurate reading. There seems to be lack of test done on each AP with laser readers)

Is single digit PM2.5 possible?

Can you really smell/feel the difference in air quality at single digit?

i only buy the cheap air purifiers (Sharp/Daikin/Panasonic). the problem with air filter is it has relatively low range as it only sucks air surrounding it and blow clean air out. also since they usually sit on the ground, that means they only suck in air close to the ground, so only the air near the purifier is cleaner. those with ionizer will cause the dust to stick on floor & walls but they will become dirty faster.


even aircon that is placed high up with good filter doesn't do much in terms of cleaning the air. however purifier with Plasma Cluster/UV like Sharp has better efficiency in killing bacteria.



so while air quality reader helps, it isn't really accurate if the room is big like living room or even master room.


so it might be better to put additional cheaper purifiers at strategic locations. the expensive ones have more function like programmable but do take in the cost of filter replacement into account. some people buy expensive purifiers but buy cheaper 3rd party filters (though can't say they are good or bad), so a air quality meter maybe good to see if these 3rd party filters are worth it.


better to figure out ways to reduce dust coming in like adding door seals, window seals, and if you open windows put some dust screen to reduce dust flow (those bug screen helps). for main door i actually use manila card as they are more flexible than rubber/brush as not all doors/floor are perfect with manila card i can position it to the lowest possible position for better seal and door won't get stuck. for windows i get those rex rubber seal as even with the original seal there are still gaps.


for sliding windows they have the worst seal as there are many gaps & holes for the wheels and very difficult (impossible) to seal.


and alot of dust actually comes in to the room from the toilet's ventilation.

and don't be surprised how much dust is hiding above your plaster ceiling because workers never clean them out after installing/hacking/drilling.

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Old 03-05-2019, 10:11 PM   #2863
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hey guys, there is a lot to read here. I'm thinking of getting an AP but not sure if it's worth the investment. Currently NEA PM2.5 reading is 17, how clean can each of the various AP models bring down from this number? (according to laser measurement and not AP's inaccurate reading. There seems to be lack of test done on each AP with laser readers)

Is single digit PM2.5 possible?

Can you really smell/feel the difference in air quality at single digit?
I posted 3 pages before on page 191. Reposting below in another post......
It could be better that you read from the end of the thread backwards, as all the latest info can be found this way.


Yes single digit is possible. Not sure why would you want that though.

No you cannot smell or feel the difference generally, unless if the external air quality is somewhat hazy. Then when you leave the room the haze smell would hit you. When you go from external environment and into the room, the difference is less.

If you are after that clean smell, start with the aircon cleaning (do DIY aircon cleaning, there is a whole big thread dedicated to that) and also change your bedsheets/pillows regularly. If you gotta hang some "used" clothes, don't hang it in the aircon and APed room just behind the door.
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Old 03-05-2019, 10:12 PM   #2864
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Below shows some March haze measurements, that time you know, pax were kpkb very smelly etc. Punggol smells (though i am living at South Part of the island)
Note, do not compare this with NEA figs.....it is what it is, bloody long story fit for another thread.


What you really want is the Air Purifier's CADR figure. This depends on the airflow and filtration efficiency. Give an extreme example, a China H11 HEPA that is only 90% effective but in a big AP that guns over 1000 m3/hr. Vs a H13 "True" HEPA 99.97% but doing only 200 m3h/hr. The former would eat the latter for breakfast.
The latter H13 AP would need to be doing comfortably over 900m3/hr in order to be equal/surpass the China H11 filter.

Note, the below is dealing with real haze. And the meter has been tested by me to be sensitive and to cigarette smoke before, which is a source that has a predominant particle size distribution as shown below.



All China H11 HEPA (measured to be 92%), except for the Mfresh M8088A which is true H12 HEPA (it's 99% thereabouts).

3 APs in the room. Mfresh M8088A actually is in lowest fan speed, coz i don't wanna load it too much. Most of the cleaning is done by the Samsung AX40 and Sharp KC-840 with China DIY HEPA, cut in size + sides stuffed with bubble wrap for sealing.

GPGT, proof that it works.
Few days ago Singapore haze.

Sudden transient peak @ 40k+ counts @ 0.5 microns


MBR (420 counts @ 0.5)



Mfresh M8088A H12, only 10 counts @ 0.5 microns lowest reading


Sharp KC-840 China DIY H11. Samsung AX40 is similar. 20 counts @ 0.5 microns lowest reading
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Old 03-05-2019, 10:40 PM   #2865
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Oh I am never concerned about single digit or double digit PMI. As long as the air quality from an average AP is much better than outside, I am happy enough. Can't be aiming for single digit and spending thousands of dollars on AP.

Sent from Xiaomi REDMI NOTE 5 on Rocket Uno with TPG Booster using GAGT
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