Thread: Interesting air quality observations...

Originally Posted by elanjacobs

In my ongoing quest to figure out what triggers my hypersensitivity to air impurities, I bought an Atmotube Pro. Based on the testing done by these guys, it seems to be the best of the consumer level air monitors in terms of both accuracy and precision.

Anyway, I've had it going for a couple of days on my belt/general vicinity and there seems to be 2 differences in the trends between home and work; one of them makes sense, the other one really doesn't.

1) Particulate matter (it measures PM1, PM2.5 and PM10) is higher at work (PM1 averaging around 6ug / m^3, PM2.5 around 10ug / m^3) than at home (both around 1-2ug / m^3). This makes sense to me, I've got a HEPA room filter permanently running in my bedroom.

2) VOCs, however, are lower at work (averaging around 0.08 ppm) than at home (around 0.20 ppm). Being an engineering shop, I was expecting VOCs to be up as well with the various solvents and cutting oils, but they're clearly not. Now I am in the manual shop, not the CNC shop, but I'm still surprised. I'll try to get some decent data from the CNC building and grinding room at some point, instantaneous measurements say it's worse, but not as bad as my nose tells me.

Any thoughts?

The concentration of anything airborne depends not only on the total amounts emitted by sources but things like the volume into which the "stuff" has to expand into, (suspect your workplace is much more voluminous than your home) and the amount of ventilation, (again suspect your work place has better ventilation).

The other thing to consider is local external airborne levels - do you live near an area of busy traffic? Tests at work showed that PM2.5s and VOC matter travels several km. We could easily see the levels rise with increased traffic from (thousands) of uni employees and students arriving and leaving in the mornings and afternoons.

If your home is properly ventilated the VOCs inside should be not that much higher than outside air. What is the VOC outside your house?

Have you checked your kitchen for particulate matter and VOCs? Processes like baking and sautéing generate lots of particles (way more than 10 µg/m^3) and if you do any grilling or toasting it will be even more again. These also produce VOCs that hang around for some time.

What this really says is that most kitchen ventilation is pretty ordinary. I've been looking at our range hood and note the external vent is basically choked with a vent that looks like this.
Screen Shot 2021-04-16 at 5.48.55 am.png

I really need to rip this off and replace it with something less restrictive.

Thanks Bob, I was hoping (ok, I was expecting ) you would chime in.

I'm in the inner-ish suburbs of Melbourne, so there's a decent amount of traffic around, especially during peak hour, but I'm 150m from a main road.

I went outside for 5 mins and VOCs stabilised at 0.10 ppm, PM1 around 6 ug/m3 and PM2.5 around 8 (I can smell someone's got a fire going).
Back inside, VOCs are 0.23 ppm upstairs and downstairs. PM1 = 10, PM2.5 = 12 downstairs, but in my filtered room upstairs it's 1/4 of that.

Haven't been doing much cooking lately (we don't bake or toast), but when dad's making stir-fry I struggle to breathe in the kitchen. It's a rental with a crappy rangehood; the air blasts out of the vent in the wall, but it struggles to hold a sheet of paper against the filter, so I don't know where the exhaust air is coming from - it's definitely not from where it needs to be.

We've got a gravity flap vent in the wall, seems to work well for airflow.

Originally Posted by elanjacobs

Thanks Bob, I was hoping (ok, I was expecting ) you would chime in.
I'm in the inner-ish suburbs of Melbourne, so there's a decent amount of traffic around, especially during peak hour, but I'm 150m from a main road.
I went outside for 5 mins and VOCs stabilised at 0.10 ppm, PM1 around 6 ug/m3 and PM2.5 around 8 (I can smell someone's got a fire going).
Back inside, VOCs are 0.23 ppm upstairs and downstairs. PM1 = 10, PM2.5 = 12 downstairs, but in my filtered room upstairs it's 1/4 of that.

You can compare what PM2.5 you are measuring with this
Melbourne CBD, Australia Air Pollution: Real-time Air Quality Index

Measurement of especially PM10 but also PM2.5 below 10 µg/m^3 is problematic unless your sensor draws more than about 1CFM when making measurements, it turns out there are not enough particles to be get accurate results.

Do you have carpets? If so they are significant dust generators. Since we got rid of all our carpets the dust levels tripped by a factor of 10.

My sensors integrate measurements for up to 30s so I can theoretically display results to 0.1 µg/m^3 not that is probably means much for very low results.

Right now in my study I have between 0.0 and 2.5 µg/m^3 for PM10 and PM2.5.
If I leave my study empty for several hours it shows steady zero for both particle sizes.

The kitchen currently shows zero for both PM2.5 and PM10 but no one has been in there for some hours.
Total number of particles counted is < 300

When the The PM10 and PM2.5 are the same that means the sensor is just not picking up any large particles.

Apart from when were cooking, the worst room in the house is SWMBO sewing/project room when she is working in there. Fabrics generate some dust but normally it does not go over 20 µg/m^3.


My VOC sensor has not been working for some time and I think I need to replace it.