Awk

I am sure there are some exceptions, but in general I think no AC do a specially good job at filtering out small particles, but even old ACs will filter out some, both small and larger particles.

I suspect the best is to research what thirdparty AC filters (filters you will use to replace the stock filters that come with the AC unit, not the disposable 3M material) are available for what locally sold ACs. Then buy one of the ACs for which you can get a good thirdparty filter for. Unlike the stock AC filters, these thirdparty filters are designed to do a good job at filtering out stuff, and hopefully there are some reviews of them available.

Why do stock AC filters not do a better job? I suspect it is simply that virtually nobody who buys an AC cares or even gives it a single thought. Certainly I did not until very recently.

We just had our neighborhood aircon guy do his annual cleaning of our 4 units and I watched him quite closely, especially the filter servicing and observed that there was quite minimal dust on the filters and inside the whole units. In all fairness, we only use the main bedroom AC 2-3 hrs a day and the others less. Don't want to get too spoiled and our house is fairly cool and location is in a remote area with a lot of trees and ricefields, minimal traffic and nearest hiway is more than 5 k away. .

The AC man remarked on the fact that there wasn't much dust and I asked him about the 3M filters and he said that they can do more harm than good in restricting air flow and making the motors work harder. He is the head of Nyom Panich [sp] air con service center and knows his stuff and is a friend and neighbor so I trust his opinion.............just sayin'

Also, my wife is a clean freak and insists on swept and mopped floors daily as well as dusting all surfaces and catches a lot of dust that way.............again, just sayin'.

I think that if we were near the city and the pollution it would be a lot worse, so I'm going to go with using the standard filters and washing them once a month.

BTW...........his cleaning procedure was to blow off the loose dust and washing them gently with dish soap and blow drying them.

I think one of the problems is that the fine particles (pm2.5 and), which are believed to be more harmful, do not quickly settle down on anything, but can remain in the air for a very long time (days and weeks). I suspect the daily cleaning will not necessarily reduce the amount of small particles in the room by any measurable amount.

I think it is also a good idea to consider that standard AC filters are usually designed to protect the AC itself from large stuff, not our lungs from very small particles, though it seems to do the latter also to some extent. Myself, I'd leave the 3M material on during this period, as even if the AC guy is right, which I suspect he is, I'd be less worried about a possibly premature repair/replacement of the AC engine than the other things.

Ok.... went this morning and now know the system....

Thanks for all your help guys, I too will keep it a secret

David

Thanks for sharing. That's the kind of posts that make this forum helpful.

Went there recently myself. The system appears to be as such:

1) Arrive before 07:30 and get in line I was there a little before 07, and there were about 25 people ahead of me in line. At this point, immigration is closed, but everyone was queueing politely.

2) At around 07:30, immigration doors open, ticket numbers are handed out to those in line, and you go inside.

3) At around 08:00, the immigration counters are manned, and they call out the number of each ticket. When your ticket is called, you go

to the counter, hand in your ticket number, show your passport, state your business, and get a new ticket number for that particular business.

4) You then wait for your new ticket number to be called, which is when your business will be dealt with.

You can of course arrive much later than 07:30 also, and take the chance that not all tickets for <your business> have been handed out, which most people do. I suspect lining up early is mostly for those doing something that takes a long time (e.g. one year extensions) with limited tickets available. Not for 90-day reports and the like.

Have your people wait on your behalf, like any rational person does.

Who would " my people" be?

Jeeves, of course.

<script type='text/javascript'>window.mod_pagespeed_start = Number(new Date());</script>

But the risk really is 0%.

What a ridiculous statement to make when these (snack size) children are sitting on reptiles, whose natural instinct it is to kill and eat other living animals.

Statistically it IS 0%. So, not a ridiculous statement at all. Are the kids in danger from being eaten by Chinchos as well? Because there have also been 0 attacks from them.

You claiming there is, statistically, 0% risk, does not mean there is no risk. It only means you have very little understanding of statistics, percentages, risks, or common sense.

I have had zero accidents driving my (bank's) car. Statistically, my accident rate is 0%. That does not mean there is zero risk for me driving the car, or that "the risk really is 0%".

I won't immediately jump to the conclusion

People like you have no place on TV.

Awk says

"I do not think that is true. I've done some measurements, and even in the very poorly isolated house I rent, there is about 20% less pollution inside than outside. Obviously, windows, walls, and doors will block some of the air, so in general it will be better to stay inside. "

​I wonder how this measurement is done ?

If one looks here

http://www.bcairquality.ca/101/measure-air-quality.html

The whole measurement process appears to be somewhat complex!

I did some measurements using a DC1700 particle counter from Dylos. The above is a vastly more thorough and professional setup of course, but with limited financial means, I wanted to get an estimate over how much closed doors, AC, and air purifier would help. For that I think a particle counter is a good device.

Staying indoors is absolutely no help unless you have some way to filter the air coming in, or filter once it's inside. Without some sort of filter system, the air inside is just about as bad as the air outside.

I do not think that is true. I've done some measurements, and even in the very poorly isolated house I rent, there is about 20% less pollution inside than outside. Obviously, windows, walls, and doors will block some of the air, so in general it will be better to stay inside. ..................

Right... So if today's pm count is 220, indoors will 'only' be about 176... Much healthier to stay indoors...

As I said, without some sort of filter system the air inside isn't any better for you than the air outside.

For those staying in more modern and better isolated apartments than old leaking houses, hopefully the improvement will be a little more. But you are right of course, both are terrible.

Staying indoors is absolutely no help unless you have some way to filter the air coming in, or filter once it's inside. Without some sort of filter system, the air inside is just about as bad as the air outside.

I do not think that is true. I've done some measurements, and even in the very poorly isolated house I rent, there is about 20% less pollution inside than outside. Obviously, windows, walls, and doors will block some of the air, so in general it will be better to stay inside.

For those without any other choice, I would recommend something like this (that is 3M's Filtrete material on the outside, available at HomePro and elsewhere):

Run it at high speed for 30 minutes or so, and thereafter for 10-15 minutes at high speed every one or two hour, or continously at a lower speed.

The actual minutes I have pulled out of thin air, but according to some minimal measurements I did last month, running such a fan/3M Filtrete setup will after less than one hour result in the particle count, and presumably pollution, in a small room being about half of what it is outside, and in the 3M Filtrete quickly darkening.

Another member here has used a different type of fan, with probably better results. Perhaps he will chime in with some details.

I originally sent this to another member via private message today, but then thought it might be of more general interest to some other people here too.

-----

...

But I was too surprised (and disapointed) that the Filtrete did not improve things more. On the other hand I was also surprised the stock AC filter worked so well, as I assume it is only intended to protect the AC itself from dust and dirt in the air.

I wonder if the result would be different if I did the measurements again today. When I did the comparison between the same type of AC, but one with 3M's Filtrete, and one without, the pm2.5 readings on my DC1700 were around 3000-5000 for the outside air most of the time. I haden't done any readings outside at home for a while, but was a little shocked when I sampled the air outside this morning and got readings in the range up to 30,000, almost ten times what it was a month ago. It has never affected me personally much, but I was curious since the air had been smelling different the last couple of weeks. It would certainly warrant repeating the measurements again since the change in air quality is so enormous.

I btw did not include measurements for my Blueair 650E in the living room, as it showed very little improvement over the room with the AC and 3M. I initially thought this was due to the living room being huge, with no doors closing of the kitchen or the second floor, as well as huge ceilings and very poor isolation. Thus overwhelming the Blueair 650E. But after sampling the air this morning, I carried one unit down from the bedroom, and noticed the particle readings in the living room dropping to a fifth of what they were before (they were above 20,000 before). A fifth is still "very poor" according to Dylos' guidelines, but an obvious improvement, so no doubt carrying the unit down in the morning and up in the evening will now have to be part of the routine.

Today, 10:00, worst of the year. My estimate based on comparison of visibility to previous years is that it was about 250+. Don't trust the readings after seeing the photo of them being hosed down.

You are not the first to mention that I think, but was there anyone with any knowledge who came forward and said there was something sinister behind that?

Surly somebody with the power to order something like that would find it much easier and more safe to just let the equipment "malfunction" during the desired period. Or just doctor the information they publish; if one can order somebody to stand outside and hose things down in order to fake things in a non-obvious way, considering they make the hourly average available, one can probably order somebody to change the published data also.

A simpler explanation would be that they were simply cleaning things.

Hi, I have now finished testing most of what I wanted to test. I will

do some more testing, but this will mostly be related to how much time

my air purifier needs to make the room clean, and what speed setting is

necessary when the pollution is extra heavy, so is probably of little general

interest.

There was quite a bit of data gathered, and so I found it easiest to use

my regular document processing system for my own thinking and analyising.

While I admittedly did not pay much attention to others possibly reading

this document when I started on it, I have tried to attach my document as a

PDF-file with this message and have tried to make it more readable for others,

in case anyone else should be interested in reading it.

My short conclusion is that the 3M Filtrete material works, and does

improve things somewhat, but much less than I expected. 3M Filtrete

simply wrapped around a fan also improves things considerably. But only the

air purifier brings the particle count down to fair level, at least without too

much noise.

Thanks for all the kind comments. I was not too proud of the quality of

the report myself (when half-way done I almost deleted it, rather than

continued working on it), but the kind comments inspired me to make some

updates to the report, and I have uploaded a new version.

Changes are:

- added table with direct output values from the Blueair 650E.

I had the data when I posted the original report, but unfortunately

forgot to include it.

- added some graphs showing how quality improves after running a brand new

AC with 3M Filtrete, and after running Blueair 650E.

Note that this is a brand new AC, located inside the city and with 3M

Filtrete installed over the original air filters. This installation

should be more "according to instructions" than how I did it with

Old AC-3M.

I also think the graphs make it much easier to visualise the difference in

effect between these two devices.

- removed my usage of PM10, instead calling it PMlarge, to avoid

conflict with the official definitions for PM10, which includes particles

of size 2.5um and less also.

No noteworthy changes to the conclusions, or previous text (except

replacing PM2.5 with PMlarge) I believe.

There are still some things I want to do. Most importantly for myself;

find the correlation between the PM10 mass reported by the

governments devices (on which the health standards are based), and

the particle counts on my DC1700, and perhaps also the correlation

between pm10 and pm2.5, but not sure how interesting that is to others.

analysis.pdf

Thanks for the replies on the child car seat. My son is 2 yrs old (11 kg) and the Hyundia H1 Van does not have isofix, anchors on the floor behind the seats nor a place for a tether to attach behind the seat. Very odd that a van which I'm sure other families have bought to transport all the kids wouldn't be able to fit even a booster seat correctly. All seats have lap belts and only the two front have shoulder straps but there is dual front airbags. Wondering if using a lap belt kind with anchor or isofix would be better than nothing or if anybody has any other suggestions. I could turn off airbag except then none could sit with and care for him as I would be driving when we take our long all day road trips.

Are you sure there is no place to attach a belt going from the rear of the child seat to the floor? Usually one can fit them around something, either under the seats in front, or on the sides. I.e., it is not designated anchors, just something solid. If not, then I do not know of anything other than the Akta Graco duologic I mentioned previously (though there may be others I do not know about of course), which is very unusual among the top brands in not requiring this. I of course think that seat is not a bad choice, and bought it due to the ratings from crash-tests, which was the best or amongst the best for a non-isofix seat in that weight group. Above 18 kg there are a lot more choices. If you want to try and see if it is usable in your car, you are welcome to send me a pm.

Btw, rear facing seats can be used much longer than up to two years. My oldest daughter is soon 6, and still sitting in her rear facing seat, which is speced up to 25 kg. My younger daughter will inherit that seat when she turns around 4 I suspect, as the Aktra Graco is speced up to 18 kg.

Awk, I'd like to suggest the following experiment (if possible) in order to determine how well rain (or a water-based filtering device) may clean air pollution:

1) Open windows in shower room for 1 hour;

2) Close windows in shower room and take particle measurements at that point in time;

3) Run shower for 20-30 minutes whilst taking particle measurements;

4) Post results here.

Since "the site and extent of absorption of inhaled gases and vapors are determined by their solubility in water", this may give us some interesting results and additional food for thought.

That is an interesting idea. Will perhaps also give an indication on what the effect of the local city workers spraying water into the air is.

I will see if I can do, provided I can seal of my particle counter satisfactory. I am concerned about exposing it to the moistness in the shower room for so long, especially since the fan on the particle counter, which I will need to leave exposed, will be drawing in moist air.

Unfortunately I do not think I will do that. I sent an email to Dylos slightly after posting the above, and got a reply back from them that they think it is likely that some condensation will occur internally under those conditions, and a subsequent risk of damage under prolonged use. Sorry. :-/

I was wondering, have you ever tested dyi air purifiers, made of a box fan & a HEPA filter (http://smartairfilters.com/#data) ?

I always to tend think that you get what you pay for, but would be curious to know if you ever tested that method, since you have a measuring device.

We used BlueAir air purifiers where we lived before and were happy with it, but considering the costs per unit, an alternative solution would be nice.

Do you mean something like the attached image? Don't laugh if not.

The fan has 3M Filtrete wrapped around most of it, and that is the only diy-thing I have tried (except 3M Filtrete on AC of course).

I included some measurements, as well as a reference to where I got the idea (from a guy who has a lot of information about a similar, but presumably

much more professional diy-setup) in the PDF attached to this post:

http://www.thaivisa.com/forum/topic/692704-smoke-smog-dust-2014-chiang-mai/?view=findpost&p=7500352Screen Shot 2014-03-12 at 8.52.11 AM.pngScreen Shot 2014-03-12 at 8.52.11 AM.png

I was running such a fan setup in one bedroom while still analysing whether I should purchase an AC with 3M Filtrete for that bedroom, or an additional Blueair unit. Was wishfully hoping AC with 3M Filtrete would be good enough for a long, long, time. Having already spent 35,000+ on one Blueair unit, I was not happy about doing it again and would much have preferred to buy a decent, and in practice much more usable, AC at half the price.

I agree that Blueair is very costly. Suspect I am paying quite a bit extra for the "Made in Sweden"-effect. Though now it is of course no longer made in Sweden. The price however is the same as it was when it was made in Sweden I believe.

Hi Awk,

Not laughing, we all try to find a solution to the pbm. What I was referring to looks a bit more "sophisticated" but idea remains the same. You probably did not get the link I posted: using a fan + a HEPA filter. Hopefully the attachment works this time.

And here are 2 links:

http://smartairfilters.com/#data

HEPA filters are more advanced than 3M Filtrete. Blueair, IQair, etc... all use HEPA filters

Well I guess, I'll have to try it for myself and buy the Dylos device to measure. Did you have to buy the device from overseas or it can be found in Thailand ?

I think the url you posted (not the one to youtube) is from the same guy I mention in my pdf, from where I got the idea.

The youtube test is of somewhat limited interest, imo, because as the guy at smartairfilters say, you need to know how the air at the output of the air purifier correlates with the air in the room. E.g., at the output of the Blueair I can get down to 20-30 particles at times, but if I move the particle counter somewhere else in the room, it will show a minimum of 10 times that amount. But it is a start of course, as if the air coming out of the purification device (be it diy or off the shelf product) is of inadequate quality, then that device probably does not work well enough for practical use. Amongst other things one needs to at least account for new, presumably dirty, air continuously seeping in of course, so the rate the device filters the air at needs to be high enough to not be overloaded by new air constantly coming in. I've worked in Beijing myself for some months, and in my experience, the quality of the homes there is much superior to the ones in Thailand, at least as far as isolation goes. This is necessary to reduce heating costs during winter of course, and presumably it also means that there is considerably less air from the outside continuously seeping in, compared to the average home here in Chiang Mai.

And no, I have not tried using a real hepa filter attached to a regular fan myself, only tried the 3M Filtrete I show in the photo.

I ordered the Dylos device from Dylos in USA, when working abroad last year. Think that is the same device (but different model perhaps) the guy at smartairfilters is using, who also seems to have published quite thorough tests.

PS: if ordering, try to get them to mark it as some sort of portable computer (which it after all is). There is no tax on that in Thailand, apart from the 7% VAT. Oh, and voltage is an issue of course.

If I remember correctly I found IC was quite expensive. While on the subject I'm looking for a baby seat for a Hyundai H1 Van. Since the back seats don't have shoulder harness seat belts nor anchors I haven't been able to find anything that will correctly fit. Any suggestions??

Is this for a very young child? At least in northern Europe, most of the larger (for children from around 13kg and up) car seats do not depend on the three point belt system, but instead do with the two point belt, and in addition usually two belts attaching the back of the baby seat to the metal frames the front seats are installed in. At least this is the case for the rear facing car seats, which is all I have looked at as I believe in the logic behind why that is safer than front facing.

If this is indeed for a very young child (less than 9 kg / 9 months?) I think one of the best seats one can get, based on the reviews I read about a year ago, is the duologic 2 from Akta Graco, which you can see here: "http://shop.carseat.se/car-seats/duologic-2.html". Unlike most other seats I've seen/used, it does not have the two belts attaching the back of the baby seat to the metal frames in front (where the front driver/passenger seats are installed), so it does not sit as tight as others, but it is still one of the highest rated seats not requiring isofix (though it does also support isofix). Our car unfortunately does not have isofix, so I had to find a car seat that does not depend on isofix, yet has good safety ratings. The duologic 2 is fitted with the two point belt system and the usual leg that extends from the back of rear facing car seats to the floor of the car. Another benefit is that it is certified up to 18kg, so if for a newborn, you will be able to use it for a long time.

I have the duologic 2 for my youngest one, and I think this one for the older one: "http://shop.carseat.se/car-seats/britax-hi-way-ii.html". Possibly the leg that extends from the back of the seat and to the floor on most (all?) rear facing seats will be a problem in a van, if the car seat is so high that the leg can not reach the bottom, so would need to check out that before buying.

I've seen some high quality car seats at Central Airport Plaza I think.

I was wondering, have you ever tested dyi air purifiers, made of a box fan & a HEPA filter (http://smartairfilters.com/#data) ?

I always to tend think that you get what you pay for, but would be curious to know if you ever tested that method, since you have a measuring device.

We used BlueAir air purifiers where we lived before and were happy with it, but considering the costs per unit, an alternative solution would be nice.

Do you mean something like the attached image? Don't laugh if not.

The fan has 3M Filtrete wrapped around most of it, and that is the only diy-thing I have tried (except 3M Filtrete on AC of course).

I included some measurements, as well as a reference to where I got the idea (from a guy who has a lot of information about a similar, but presumably

much more professional diy-setup) in the PDF attached to this post:

http://www.thaivisa.com/forum/topic/692704-smoke-smog-dust-2014-chiang-mai/?view=findpost&p=7500352

I was running such a fan setup in one bedroom while still analysing whether I should purchase an AC with 3M Filtrete for that bedroom, or an additional Blueair unit. Was wishfully hoping AC with 3M Filtrete would be good enough for a long, long, time. Having already spent 35,000+ on one Blueair unit, I was not happy about doing it again and would much have preferred to buy a decent, and in practice much more usable, AC at half the price.

I agree that Blueair is very costly. Suspect I am paying quite a bit extra for the "Made in Sweden"-effect. Though now it is of course no longer made in Sweden. The price however is the same as it was when it was made in Sweden I believe.

Awk, I'd like to suggest the following experiment (if possible) in order to determine how well rain (or a water-based filtering device) may clean air pollution:

1) Open windows in shower room for 1 hour;

2) Close windows in shower room and take particle measurements at that point in time;

3) Run shower for 20-30 minutes whilst taking particle measurements;

4) Post results here.

Since "the site and extent of absorption of inhaled gases and vapors are determined by their solubility in water", this may give us some interesting results and additional food for thought.

That is an interesting idea. Will perhaps also give an indication on what the effect of the local city workers spraying water into the air is.

I will see if I can do, provided I can seal of my particle counter satisfactory. I am concerned about exposing it to the moistness in the shower room for so long, especially since the fan on the particle counter, which I will need to leave exposed, will be drawing in moist air.

was there not a similar thread to this a few weeks ago in this forum discussing poor service from a hua hin based furniture seller, and the OP had been warned not to name the company as it is against forum rules

yet this thread is allowed to stand, and people are allowed to discuss negative experiences they have had with this particular retailer

why is this thread allowed, whereas the furniture one was only allowed to stand as long as he did not name the retailer?

What is your point, exactly? That you want someone to close this thread? If not, why not simply keep silent?

Interesting thread. I had the impression, wrong or right, that Powerbuy was part of Central, which in my very limited experience (one product) do know the stuff they are selling impressively well. Seems it was good luck that when I last month purchased some very expensive home appliances and went to Powerbuy first, they did not sell what I wanted to buy. Even though it was listed on their website. After reading this thread, I'll make sure to stay clear of Powerbuy.

Lots of people recommend HomePro, so going with them when I can for now.

Very interesting...

So to summarize, an a/c with Filtrete material does a good job of removing the larger PM10 particulates, with average results for PM2.5 removal. The dedicated air filter does a great job with both, according to your results.

More on atmospheric particulate matter here.

Well, perhaps, depending on what you think average results are.

To tell the truth, I am having a lot of trouble getting anywhere close to the "fair" air rating quoted by Dylos when I measure the effect of the AC with 3M at my friends apartment in the city. The Filtrete is presumably working since the particles larger than pm2.5 are much reduced inside compared to the outside, but I see very little effect on the pm2.5 and smaller particles. But I will wait till I have analysed more of the data before I conclude anything. I should also remove the Filtrete from the AC in the city and do some measurements on the AC without Filtrete, like I did in house. The city AC has something called "Virus Doctor", which is supposed to have some extra air filtration effects (and perhaps hives of harmful ozone too? Dunno. :-/) Will see what I have time/motivation to do.

my hack is to to use 2 layers of Filtrete over the intake which is on top of my unit.

I use small amount of tape to hold down the edges.

Just off the cuff measurement where I put my eye ball near the A/C's outflow and notice less eye irritation than using the filtrete over the internal filter. My theory is don't suck dirty air into the unit at all.

I might try adding a layer to internal filter next for a total of 3 layers.

Cool experiment Awk has shared. What is the measuring unit? cost etc?

Well, at least you are basing your opinion on something real, though one should of course reproduce the eye ball experiment by also using two layers around the internal filter. ;-)

The unit I use is a DC1700 from Dylos. Their website is |http://www.dylosproducts.com/" and you can see the costs there. If you plan on ordering one, perhaps it could be marked as "laptop" or "portable computer", which have zero tax in Thailand, so you only have to pay the 7% VAT I believe. Must be careful about the voltage difference though.

Such a unit could be quite useful for testing various ways of attaching 3M's Filtrete I suspect. I.e., hopefully the effect of using two layers of Filtrete on top of each others is not similar to the effect of using two condoms. ;-)

I btw have noticed when googling that 3M produces a range of Filtrete products with different ratings, some with a much higher rating than what I see for sale here at e.g. HomePro. Presumably they will do a better job at filtering the smaller particles.

Check the defininitions of PM10 and PM2,5

All the ones I find for PM10 are inclusive of PM2,5.ie,,,pm10 is all particles 10 microns or less. The only definitition I found that differed is the range given by your meter website. There they do say the ranges roughly equate to the PM10 an PM2.5

The numbers I have used are for the definitions I stated above. I.e., pm10 does not include the pm2.5 particles.

If what you say is correct, which I have no reason to doubt, then I must certainly change the terminology I use to avoid confusion with the official terminology, or possibly include the pm2.5 count in the pm10 count like the official definition does. Will have to think a little about what is best to do. Thank you, I was not aware of this.

my hack is to to use 2 layers of Filtrete over the intake which is on top of my unit.

I use small amount of tape to hold down the edges.

Just off the cuff measurement where I put my eye ball near the A/C's outflow and notice less eye irritation than using the filtrete over the internal filter. My theory is don't suck dirty air into the unit at all.

I might try adding a layer to internal filter next for a total of 3 layers.

Cool experiment Awk has shared. What is the measuring unit? cost etc?

Well, at least you are basing your opinion on something real, though one should of course reproduce the eye ball experiment by also using two layers around the internal filter. ;-)

The unit I use is a DC1700 from Dylos. Their website is |http://www.dylosproducts.com/" and you can see the costs there. If you plan on ordering one, perhaps it could be marked as "laptop" or "portable computer", which have zero tax in Thailand, so you only have to pay the 7% VAT I believe. Must be careful about the voltage difference though.

Such a unit could be quite useful for testing various ways of attaching 3M's Filtrete I suspect. I.e., hopefully the effect of using two layers of Filtrete on top of each others is not similar to the effect of using two condoms. ;-)

I btw have noticed when googling that 3M produces a range of Filtrete products with different ratings, some with a much higher rating than what I see for sale here at e.g. HomePro. Presumably they will do a better job at filtering the smaller particles.

You can say all the justification that you want, but the FACT is the two tests were not done under the same conditions. Why not reverse the test then?? Start with a dirty air filled room, let the stand alone run for 50 mins, then turn on the aircon for 20 mins. At least if you had shown that you did the same test, two different times it would appear more logical.

Regardless, I don't really care that much about the results, as I feel what we have cleaning our air is suffice. And the following saying keeps popping into my mind…."when you wrestle with a pig you both get dirty".

I wish you continued entertainment / enjoyment with your (skewed) experirments. Geek on bro….

Well, I have done that too. The problem is that when I do that, the air inside the room gets gradually dirtier. The AC/3M combination is not able to keep the particle count down to the level the air purifier kept it. This must of course be because the (much dirtier) outside air is continously seeping in, whether the air purifier or the AC is running. The AC/3M combination unfortunately has no chance at keeping the particle count down to the level the air purifier keeps it. Instead of the graphs showing the particle count continuing to drop once I switch from Blueair to AC/3M, the graphs shows the particle count raising drastically for the pm2.5 count. The pm10 count does not change much, so the AC/3M does seem to do a comparable job at filtering that.

Regarding sayings popping into one's mind, I admit I also have had one popping into my mind during these conversations with you.

“Never argue with an idiot. They will only bring you down to their level and beat you with experience.” George Carlin I believe.

Not sure what your continued references to "geek" are, but coming from you I guess I should take it as a compliment.

What I do have trouble understanding is that I believe pm10 refers to the number of particles less than 10 microns which also include the 2.5 micron particles so I can see why the aircon filters reduce the pm10 but take out less of the 2.5 micron and smaller and iin your graph the bluesky seems more efficient on 2.5 than it is on the larger particles. Why?

Hmm, yes, the pm10 count refers to particles less than 10 um, and does not include the pm2.5 particles. I.e., the pm10 count represents the particles larger than 2.5um, but smaller than 10um. The pm2.5 count represents particles between about 0.5um and 2.5. (0.5um is the stated detection limit of the DC1700 particle counter I use).

Why the Blueair seems less efficent than the AC on the pm10 particles? That is an excellent observation.

The reason for this I believe I explain in my 2) point in reply to VIBE's post a few minutes ago. As you see, the AC/3M combination has already done a pretty good job at reducing the amount of pm10 particles at the time the Blueair is started. I.e., when the AC started, the PM10 count was over 300. By the time the Blueair is started, the PM10 count is only around 40 or so. There isn't all that much more the Blueair can do at that point. Even if it were to completely eliminate all PM10 particles, it would still only result in a reduction of 40. Nothing compared to the AC/3M combination's reduction of 260+.

So as I said in my other reply, this graph is quite unfair to the Blueair, as the the results are very much skewed in favour of the AC/3M combination.