In this post I will share my experience with measuring Dust Levels using my vThings Dust Monitor in my home city Sofia in Bulgaria and using my two Air Purifiers – BlueAir 450E (450 eur) and Xiaomi Air Purifier 2 (160 eur).

This is the 3rd post in the “Dust Levels” Series. If you haven’t followed them, it may be worth taking a look a the previous posts as well:

• Why Measure Dust Levels? 
• How to Measure?
• Protecting your home (this post)

Due to lot’s of factors (city is in a valley, less wind during the winter, heating is predominantly coal-based) we do often get pollution levels above 300 ug/m3, with an agreed daily average below 50 ug/m3. Long time I was living with the assumption that as long as windows are closed, the dust will eventually settle, regardless to the outdoor pollution level. Once i started measuring using my Dust Monitor, unfortunately it turned out that i couldn’t have been more wrong. Tale a look in the below chart. It illustrates dust levels measured in a 12 m2 room.

Several scenarios have been measured one after the other, on the chart above.

• Window is just partly opened (outside pollution is ~250 ug/m3). As you see it takes ~10 hour to pollute the whole room (though, have in mind you don’t want to spend more than 1 hour on any concentration above 50 ug/m3)
• Window is fully opened – Surprisingly it takes a couple of minutes to pollute the room. Unfortunately, this is not enough if you want to release built up CO2 (you may need to open all windows for 10-20 minutes to decrease it to <500 ppm) (sadly i do not have yet an example for this)
• Air purifier is running in low mode (almost you can’t hear it) – in about 1 hour the levels drop <10 ug/m3
• Air purifier is running on max power – quite noisy, but it takes 15 minutes to clean up the room
• Air purifier is not running – The dust level decreases, but this is because the  air in the remaining part of the apartment is <30 ug/m3 so to creeps through the door

Now, interesting – how this scales for the whole apartment (130 m2):

• 18:00 – we are back from work. Start cooking (turning on the cooking hood (sucking polluted air from outside)
• 19:00 – outside pollution slowly starts rising from 250 -> 400 ug/m3, which also increases internal dust levels
• 20:00 – Internal dust levels are now 150+, measured in two parts of the flat. Now i turn on the BlueAir 450E on max power
• 22:00 – within two hours, dust levels are <40ug/m3, but now i decrease power to 50%, to reduce noise.
• During the night – it is quite interesting how, even if the BlueAir is running on 50%, in the room where it is located it barely keeps the 40 ug/m3, but in the other room on the other side of the flat – the dust levels rise up to 65 ug/m3 in the morning
• If we hadn’t turned on the Air purifier, we would have been sleeping @ 200+ug/m3 which is 4x the average daily norm of 50 ug/m3

So as you can see if you want to breath clean air (at least at home), getting a purifier is a must. This way you can ventilate your house to let bad indoor air out, and then – still have clean air to breathe. Of course – this comes with a price. The BlueAir 450E costs 450 eur (interesting how they matched the price to the model number!), and filters may need to be changed each year (depending on usage patterns.. according to the spec they are rated @ 180 days). Which costs ~100 eur. At the end – if you want to have safe environment at least at home – i believe this is a fair price. The purifier is rated for 45-60m2 rooms, but as you can see – it manages to cleanup a 130 m2 flat reasonably well. The other drawback is size. This is how big it is (picture is from their official site)

Another interesting alternative is the Xiaomi Air Purifier 2. It costs 130 Eur (i even got a promotion for free shipping with DHL) 30 eur import fees, so totals at 160eur. For now i do not have charts with it (i got it two days ago, and now the air is clean 🙂 ). But in the first run, it was also able to purify the whole apartment (decreasing from 150 ->50, with outside pollution >400 ug/m3). It comes with a nice mobile app, so that you can control it remotely. It also measures pollution levels. (have to still verify how correct they are).

It is ~3x smaller than the BlueAir. So at full power it had hard time to clean up the whole apartment, and coudn’t decrease to lower than 40ug/m3. It is also quite nosier at full power. But the benefit is that it can be controlled from an app, so in fact- you can turn it on 2-3 hours before you come home and let it clean the air.

Once the air gets polluted again i will post some details about it.