** Update 12/8 ** I've updated from 2 stars to 4

I had to post an update because of the amazing customer service.. it wasn't immediate but it was efficient. I honestly didn't expect much at all and was planning on returning my device. I did not and here's why..

I purchased during the CA wildfires so I could not calibrate the device and it was inaccurate. So, if you are buying during bad air quality outdoors it will not be accurate, though will still show you if things get better or worse until you can.

Once I calibrated to the "fresh" outdoors a couple weeks later when our "hazardous" (worst in the world) air became "fresh" I could spend more time working on calibrations.. it took several attempts and did this over several days (2 weeks) in an effort for consistency. I did have to adjust manually but the online eBook was helpful through the process.

I'm not sure I totally believe all of the HCHO are totally accurate as I know some essential oils that actually aid in respiratory health and if nearby will set the monitor off, then dissipate over 10-30 min and the machine is happy again. So, some things heavier than air will register.. know what is nearby and make your own conclusion as to your safety of the air.

The PM2.5 which is huge for CA wildfires and to me, with a respiratory medical disability is most important. It is quite accurate though once you finally calibrate. Because of the time it took me to calibrate and believe the unit, I didn't want to return the unit. What I found out was that it's difficult to find machines that will show US guidelines so you will get a green, yellow, or red face on your machine. Just know, it is still green when it should be yellow/orange in US guidelines. I was willing to keep the unit for a discount for all of these difficulties and the company came through and compensated me more for my troubles.

I've upped my rating from 2 to 4. My reason for not a full 5 is because of the time to actually get things working as they should and the fact I basically have the US standards memorized, I can't always count on the happy green smile to be good for my own health. The readings however, are pretty much dead on now (outside) with EPA reports. I do believe your results will be accurate, however you may need to decipher them to US standards or your own personal sensitivities. The company is very receptive to questions and offering a response.

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ORIGINAL POST

I purchased this during the CA wildfires when the air quality was in the "Purple/Hazardous" zone on the US charts (see my last photo for US PM2.5 values). Our air quality PM2.5 was over 300 ug/m3 but this tester showed a yellow "poor" face. Since you can't calibrate it indoors, I had to wait 12 days to get a good air quality day. I've recalibrated the machine at least 5 times. The time apparently resets each time you do this too so the time is always back in 2015.

I give the unit 2 stars because after calibrating is is moderately accurate. Not enough to use to measure actual air quality standards, but it will fluctuate when put near harmful products enough to know there are VOCs around. The fact it tests for formaldehyde is cool too, but I'm not sure about the accuracy as it jumps from green to poor and back for no apparent reason.

Photos in order:
The first photo is show what my unit looks like purchased at $109. I clicked in the link to review earlier today and this model ( https://www.amazon.com/dp/B074FTVHFN/ref=dp_prsubs_1) showed up with all the same reviews and comments as the model I have. Hmm As I review this afternoon, the image again shows my model purchased. Just be aware what you are purchasing.

Second photo is after all of my calibrations on another day the PM2.5 was reported by the EPA here as 57 which is unhealthy. The unit read 54, not too bad. The PM10 was off considerably. The biggest issue I have is that after reading the manual, I finally realized why the unit kept saying "normal" when it was "unhealthy" by US standards. The unit goes off the China air quality chart (see photo 4 from manual). Photos 3 and 4 show air quality taken at the same time as the monitor indicated in photo 2. For this reason, the unit is not useful to me as someone with respiratory issues that needs the US air quality results. See last photo 6 for US standards chart and compare to what you will actually see with the unit on photo 5 China standards chart.

It's just too far off for me and I'm not going to figure it out on my own, though one could. I contacted the seller 3 days ago as their email said to do that before posting a negative review but have heard nothing back. My request was asking how to change the unit to US standards if it's possible at all. If that can't be done, I will be returning it. I'm hoping this review will prompt a response, otherwise the unit is going back.

I almost died.

But first, I cannot recommend this enough for pet bird owners who necessarily must be paranoid about air quality for all species of pet birds. Their efficient respiratory systems are exceptionally sensitive, hence the inhuman practice of using canaries in coal mines to warn of deadly chemicals.

When moving into my new apartment, I was originally excited to hear that the natural wood floors were refinished. Unfortunately, the contractors were so low class it was right before I moved in. I already had to move my pet cockatiel to my brother's apartment for the big move. Had I not, the bird would have surely died. I ALMOST DIED. When sleeping in the apartment for the first time, I woke up nauseous, exceptionally confused, and dizzy.

The constant plastic jar smell made me buy this device, still more concerned for my bird. When I received it, the monitor boomed up to HCHO .500 with VOCs at 7.500. That didn't seem right. I calibrated it on my balcony. After the fresh air nulled the standard, I tested again. I got the same result! The EPA officially says it's because my apartment is hot from the plentiful sun, sealed windows, and low humidity, caused the formaldehyde to off-gas like an oven.

Since then, I have taken steps to manage formaldehyde spikes and everything-else spikes from the July heat. I mainly open windows with battery powered fans (OPOLAR brand) that work past power outages: one side of the house has intake fans and the other side of the house has exhaust fans. Charcoal bags, air purifiers, and air purifying plants only made .010 of an HCHO difference"”with this device letting me know! Only venting gets the sin out.

It is bright, decent battery, stands up well on the stand. I love plugging it in and checking on it in the center kitchen. The alarm is actually useful for local notification because it beeps when fresh air changes to less fresh air, "Unqualified," as pollution. Helps you understand if what you're doing is effective.

I recommend only the original gray model. They all have different user interfaces. The seller needs to divide them into different pages. I bought the white model because it had humidity and temperature as well. When checked against a more dedicated Grovee temp/humidity monitor, it was always approximately 5-7 degrees off and 10-12% humidity off: too much to be useful. Its HCHO and VOC was precise, but it had no alarm.

What would make this amazing is wifi notifications along with IFTTT integration to exhaust the house when levels are high. Radon testing would be the best.

I was suffering where I work - it is a really small company and the ventilation is never very great and sometimes just bad, and the air gets stale and carries various stink and polluting materials and the wrong temperature and too humid or too dry - I bought it to give some sort of objective view, and backup to my whining and my resulting bad behavior! ... It seems to have given me some peace of mind, a little bit. Obviously the owner wants to save money by letting in just a minimal amount of fresh air. The HVAC system seems not to have been developed by the greatest of engineers ...
So I bought this and it does apparently work fairly well!

I wish that it could have a way to NOT show a big bright yellow or green smiley face or frowny face, because that made some people think it was to test your breath, or tell if you were drunk, or whether it thinks you are pretty (I think they thought there is a camera on it)

My greatest fear about it is that I will leave it out and then someone will take it and then I will never see it again, but there is no way that anybody could build a thing that would not have this problem. Some kind of bicycle lock for it maybe ???

For a design idea, i thought maybe it would be smart to allow the user to specify a session for data recording - make it so I can tell it i'm going to leave it out for 20 minutes or 8 hours, and please keep a record of the average every 5 minutes or every 30 minutes or whatever - it might be tricky to make it usable - something like a microwave keypad or just choosing from a list of intervals maybe. The way I used it in lieu of this was just to glance at it periodically and take a photo of it with my cell phone camera. Also obviously writing it down in a notebook would be easy.

I noticed whenever I turn it on it shows high readings at first if it has not been turned on for a while, because of the plastic case making some kind of measurable gasses. But it can detect the difference between fresh outside air and stale inside air.

It helped me also at home because I turned it on in our bedroom and it showed high formaldehyde so now I realize it is good to run our filter or leave the window open a crack.

One downside to the sharp edged 1.0 detection level is that it seems to think 0.95 is just really completely fine and I suspect 0.95 is almost as bad as 1.05 but the readout looks completely different emotionally then. I doubt the 1.0 level should really be that significant.

I noticed acetone nail polish remover seems to affect the formaldehyde reading. I didn't find that to be a big issue but it could be confusing to try to diagnose what is going on in a nail salon if the user doesn't realize it.

I would have preferred a carbon dioxide reading also but apparently from what I read the air would have to be really extremely stale in order to see a reading that would be a medical issue. But I have read if it is about 800 parts per million (double what is in the air) it can start to make us humans sleepy and make more mistakes. But it would have doubled the cost of the detector or more, since it requires a complicated chamber with a special detector electronics in it.

Hope this helps!

Its not industrial quality and I do not believe it is designed for that kind of environment, but it is good enough for casual use. I leave it outdoors to get a number as a baseline and then use it at home and at the office.

UPDATE:
I've uploaded four pictures of a less expensive monitor available here on Amazon (on the left). And the EG AQ Monitor is on the right. YOU decide which you'd rather purchase.

This meter helped me discover there are unhealthy levels of formaldehyde in my bedroom. I criticized the seller about not making the ebook easily available. They sent the link to that ebook pronto. But it turned out to be much ado about nothing. The ebook doesn't really address how to use this particular meter.

When the meter first arrived, I calibrated it by going to the library late Sunday night. IOW, a place in town where there were absolutely no cars driving around at all. I live near a highway and the amazing thing I learned is, the pollution from the cars is negligible. Whereas, the pollution INSIDE my apartment is a BIG problem.

There are tweaks you can make such as how bright the readout is and how long it stays on before automatically turning off. Also there are (supposedly) ways to record historical data. I haven't been interested enough to learn those features yet.

What I appreciate the most is that, once you get used to it, the meter is VERY EASY to read. Instead of worrying about the numbers, the main thing is whether any of them turn RED. So long as everything's green, all is well. I've investigated the thresholds of the meter against what health agencies recommend as thresholds and they match. So if a number turns red, you know that particular contaminant is definitely above what is deemed to be a healthy level.

As I said previously, I'm getting red readings for formaldehyde. Turns out a LOT of modern products generate formaldehyde, even furniture. I'm thinking my bed is the main culprit. And since I paid over five thousand dollars for it, I'm not happy. Turns out all of that sleep comfort crap has a secondary effect on your health. I'm writing this paragraph to help you understand, it's VERY possible you have unhealthy levels of formaldehyde in your home and don't even know it.

Is this the most accurate air quality meter in the world? I have no idea. I only know it confirmed my suspicions that there was a suppressive element in the air within my apartment. And it eased my fear of being exposed to exhaust from cars.

Due to the way it's designed, you don't have to be an air quality expert to derive benefit from this meter. I bought another meter that includes CO2 readings. When it arrives I will compare the readings and then I'll be able to comment on the accuracy of this meter.

Happy So Far.