mindstalk | Entries tagged with air quality

Last week I was in crowded elevators in a medical building. Masked in N95 of course, but still, risky. And this week I thought I was having incipient cold symptoms: one nostril almost congested, a bit of throat tickle, general blah-ness and lethargy. My covid tests were negative, though I don't know what sensitivity to expect at such a minimal symptom stage.

Then I looked at pollen.com. Pollen levels are low (3-4 on their index), but non-zero, with grasses, a known nemesis, listed as second component. And it was really windy for a couple of nights (almost as if the weather were angry), perhaps driving air into the house. Hmm.

So I restarted my air purifiers before going to bed last night, and today, I feel great! Clear and energetic.

I don't know if it really was grass pollen. Could have been dust mite buildup, or some sort of mold. Due to falling temperatures the house has been more sealed than before (mostly meaning I'm not running a window fan all the time anymore, and closing more windows.)

But one way or another, clearer air was followed by better health!

Could also explain why I felt better yesterday afternoon, on a walk, than yesterday morning. Either pollen (and wearing a mask helped) or something in the house air (and being outside helped.)

[The post title is a reference to reports of many people insisting that their hacking cough is just some sort of new allergy, even in snowy December, and couldn't possibly be covid-19~]

So I like my new Levoit, and they seem good overall. But there's something to look out for. If you find a page comparing their many different models, you might scan down, and see something like

Core 200S -- 176 sqft -- $89 -- 7 pounds

Core Mini -- 176 sqft -- $49 -- 2 pounds

and you might think the Mini is a great deal. Or you might smell a rat and dig deeper. And if you dug, you would find that Levoit is coy about the CFM/CADR of the Mini, but buried somewhere you can find a line saying it's 2 changes of air per hour for that 176 sqft. Whereas all the other models are rated at 4.8 air changes per hour. Which means the 200S is around 112 CFM but the Mini is 47 CFM. Not such a great deal.

Lesson: don't choose a purifier until you've really pinned down its CADR, in whatever units you like. "Covers a room of size X" cannot be trusted unless they also say how many air changes (ACH) that's for.

I view this as shady on Levoit's part, but then the whole market sector is a mix of good engineering and shadiness. You've got people selling basically the same thing for 2 or 3 times the price. You've got add-ons that don't work or are outright dangerous (ionization and ozone-generating UV).

I should also note that I wrote most of this based on memories of their own website. On Amazon, I see the 200S sold as "ideal for 183 sqft" in the fine print, but the headline is "up to 915 sqft" -- which only works at 1 air change per hour...

while, heh, the Amazon Core Mini page has an explicit 46 CFM for the Mini vs. 140 for the 300. So now it looks not so much disappointingly shady as just inconsistent marketing.

(Though I also note the Mini is "HEPA" and not "True HEPA". Another thing to look out for. And has an aroma dispenser which I wouldn't want.)

Ordered this last night, arrived this morning. Amazon is good at what it does...

Supposed to weigh 6-7 pounds, but it's _bigger_ than I envisioned. I was expecting something slightly larger than a personal air purifier, this is much bigger. Not sure it would even fit in my backpack and if it did, it would fill most of it. Traveling with it would be somewhat awkward. Could maybe do it if I dump my winter stuff, or else expand to a second piece of luggage.

The top speed is loud-ish (supposedly 50 dB elsewhere) but a lot quieter than top speed of my Honeywell 50250. Possibly quieter than the quiet mode of the Honeywell. Of course, lower power: 140 CFM (cubic feet per minute) vs. 250, for the top speeds. It may also be that the Honeywell needs a filter cleaning.

Power: top speed took 15 minutes to reduce office PM2.5 of 7 to under 1.

It has 3 main speeds, and a night mode. Low speed is definitely audible but not big. Night mode is almost silent, but then I wonder how much it's doing. There's _some_ air flow. Sadly, none of these purifiers or fans seem to give ratings for less than top speed.

Why I did order this one? It seemed small plus rated as both cost-effective and quiet on graphs like this: https://twitter.com/marwa_zaatari/status/1598180050893148160 or https://twitter.com/LibDemPatrick/status/1598460782408351744
And double checking myself, it had CFM/$ of around 1.4, with little in the HEPA space beating that, apart from discounts. (I did find later that Taotronics is having a huge sale on one, 176 CFM for $60. Sale like that might mean they're discontinuing it and you should buy your replacement filters now.)

By the way, it's been maybe 20 minutes on low (not night) speed and PM is still under 1, so it's keeping up with whatever's leaking in. Probably too soon to really tell, though.

I have two purifiers currently. A Honeywell 50250 HEPA. And a 12x12 inch MERV 13 filter I taped to an Amazon Basics fan for DIY. I didn't expect the latter to be great, but I thought it was doing something. Now, I have my doubts.

A few days ago, office measured PM 7, I ran my DIY. After 45 minutes PM was 2, woo? But then it stayed for the next couple hours, so I'm not sure that wasn't just air variability.

Today, PM was 6+; with the Honeywell, it was 0-1 within 15 minutes. (I'm not sure my QingPing can measure <1 without wobbling.) Later I paid more attention, and even on low mode, PM was under 1 in 10 minutes.

Then I wondered how my DIY would do against high load. I fried one strip of bacon... and overshot; PM went to 999, which as high as my monitor goes. Oops. I moved the DIY in, closed the door, and waited. After 20 minutes, it was down to 893, and I wasn't sure if that wasn't just leakage/escape. Thing is, the kitchen area isn't that big (though that's complicated by literal holes in the interior walls.) 1000 cubic feet and 40 cfm should still cycle most of the air in 25 minutes, and hopefully reduce PM by like half (MERV 13).

Then I tried the HEPA. After just 1.5 minutes PM was 750. 9 minutes, 200. Whoosh.

I wondered if maybe DIY had done the hard work of getting under 999. Switched. 6 minutes, PM maybe went from 155 to 148. What if I ran nothing? 10.5 minutes, 148 to 140. So the DIY is maybe doing something, but just 2x natural leakage.

I then worried if the HEPA was biased: it blows straight up, and my monitor was on top of the fridge, near the stream. So I moved the monitor, and numbers stalled for a bit, but still, 140 to 48 in 5 minutes.

Honestly, given the volume and CFM, the Honeywell seems maybe too slow: it should be cycling the air every 4 minutes, and through a HEPA filter! But it's undeniably faster than this DIY.

A well made DIY, like a Corsi-Rosenthal box fan, is said to be very powerful, like 250 or even 400 CFM, for cheap. Maybe, but I sure didn't touch that. And if I ever do build another one, I'll want to test it, just as you should fit-test respirators. I wonder if I can get a particle source other than frying something or making popcorn.

Relatedly, I ordered a Levoit Core 300, for use in another room, and future travel. _Then_ I signed up for Consumer Reports, to read their air purifier reviews. They gave it low numbers... but also, I was not impressed with their reviews. They give high ratings to big purifiers with low CFM/$. They don't give precise numbers of their own, like CFM ACH or CADR. The more detailed Levoit reviews actually seemed great -- bunch of pro, no cons. So why the mid ratings? Totally unclear Also one of the reviews said "rated for 0 square feet" which uhhhh.

Where's the site that will tell me if CR has gone downhill?

So that Vitalight monitor got real use today, as I went and endangered myself.

Met a friend at a taqueria, eating outside. Not a ton of risk there apart from having a traveler talk at me. I was checking out of curiosity, registered 750 ppm at one point but that's probably from being between 2 people talking. But then I went to use the bathroom and that was also in the 700s.

Then I went to an alumni meetup, in a bar, though very well ventilated; CO2 around 600, nice. I still stepped out to drink some water, CO2 means less when people are talking at you.

Afterwards I passed a donburi place with lots of room, no customers, and an open door, and got tempted to eat there, by the door. CO2 around 550-600.

Finally the bus home, which scored as high as 1100, before most people got off and it started slowly coming down again. I guess the ventilation is slightly more powerful than 3 seated people exhaling. Gee, must be really fun when really crowded. One of the newer buses so you can't open the upper windows.

So, how do I feel about the QingPing, now that I've had it for over 2 months? I'm still happy with it. I trust the PM2.5 and CO2 sensors. Less sure about the VOC, which seems to shoot up and down for unclear reasons... and if it's accurate, this house is eeeeeeh. It reads particularly high over night in my bedroom: closed windows, placed between newish foam mattress and the wall for charging.

We recently had a week of bad air, in a way worse than Mexico City, where the PM comes from cars so gets better overnight, while this was just a blob of woodsmoke or something. So I got to experience the juggle of balancing low PM (close windows, run purifier) vs. low CO2 or VOC (open windows). The purifier -- Honeywell 50250 -- is actually powerful enough to make a dent even with the window open, like levels might be 30 mcg outside and 10 by my bed.

Last night I pan-fried some ribeye steak. I aimed for a good sear, so I had the pan on near-maximum heat. (Gas stove.) I got a lot of browning, but also kitchen PM levels in the 200s. After airing it down to 60, I pan-fried some potatoes, on lower heat, and at first that was stable, but I went away to read for a bit and let the potatoes blacken somewhat, and PM shot to the 400s. I went in masked, loaded a plate, and took it away to eat.

Tonight I pan-fried a pork chop. Given that I want a higher ratio of cooked interior to crust, I stuck to medium heat, and that helped a lot; PM didn't go above 17 even after the formerly brisk breeze outside died down. Then I made some popcorn in a saucepan, and things were mostly good until the end: the price of waiting for recalcitrant kernels to pop is risking browning or burning the ones that already have. I think PM passed 100, certainly passed 44.

A kitchen with a proper vent would help, though that's largely exporting the problem outside. I'm now wondering what _happens_ to particulates in the long run. Does anything actually remove them from the environment?

I finally ordered a more portable CO2 monitor than the QingPing pro. Main choices seemed to be the Aranet4 or Vitalight Mini; while I have enough income to blow $250 on a single-purpose toy, I don't want to, so I tried the Mini.

Review that helped push me over, and guided my initial use: https://breathesafeair.com/vitalight-mini-co2-detector-review/

I was rather grumpy at first; I didn't understand its behavior. I think that it was reading around 100 PPM lower than the QP, and in my well-ventilated room, that often meant it was trying to go under 400. Per the review, I did multiple manual calibrations, in particular I reset _both_ monitors in the same place at the same time outside -- and in a cross-breeze, rather than right by the door where it's recessed, at first. That got them both yielding similar values, and plausibly low ones where they should.

Yesterday I finally took the Vitalight out for a walk (it's been raining a lot) and measured CO2 at the public library and in Safeway. Mostly in the 600-800 range; there was a burst of 3000 at the pharmacy counter, but I might have been breathing in its direction, and it's quite sensitive to that.

Is 800, or even 600, indicative of enough ventilation to be able to attend unmasked? I dunno. Maybe, in a quiet area. In a talkative area, less so.

Related paper https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8043197/
and spreadsheet https://docs.google.com/spreadsheets/d/16K1OQkLD4BjgBdO8ePj6ytf-RpPMlJ6aXFg3PrIQBbQ/edit#gid=519189277

How does a $40 sensor manage to compete with a $250 sensor?

Cheaper brand of NDIR, with +/- 50 ppm instead of +/- 30.
Doesn't measure pressure or temperature or humidity.
Doesn't keep a record of readings or connect to wifi or have an app.
The Aranet was actually just $150 before the pandemic, so 40% of the price seems to be profit-taking...

The review complains about a weekly automatic recalibration, with the advice of taking the sensor out for a walk at least that often, otherwise it may take a high indoor baseline as '400'.

Anyway, I'm fairly happy with it. I figure it 'only' having 8 hours of battery life, and even the recalibration thing, might be avoidable by leaving it off except when I go somewhere, which isn't that often.

After much dithering about CO2 and air quality monitors, this review got me to buy a QingPing Pro. It does PM2.5, VOC, and CO2, plus temperature and relative humidity, for around $150, and light weight. It came today, and I've been paying a lot of attention to my new toy.

Also, I have a DIY air purifier, a 7 inch Amazon Basics fan, with a 12x12 inch MERV 13 filter duct taped to it. I also have a large Honeywell purifier hauled up from the basement, of unknown history.

The monitor is not obviously inaccurate; reset and near an open window, it had low readings compatible with IQAir and Purple Air, around 2-3 mcg/m3. Put in front of my purifier, and it dropped to 0.0-1.0, after what seemed a 20-25 second latency. Put above the Honeywell, and the readings rose to 5+, suggesting something wrong with that (contaminated from past use?) but at least there's a difference.

Breathing on it makes CO2 jump after 10 seconds, though come down much more slowly.

Running my gas stove made no PM difference, though pumped up CO2, but it seems the main pollutants of gas stoves are NO2 and CO.

Later, the PM readings rose, followed by a smell of smoke outside. Hmm! So I closed the windows and door of my office, with the DIY running. After 90 minutes, the room's readings are under 1.0. The system works! I'm somewhat surprised, since the airflow through the filter doesn't feel high, and I wondered how much filtration is being done -- but apparently enough to clean the air to probably the sensor's error zone.

The VOC took 4 hours to calibrate, but finally started up in my bedroom, with VOC of 0.4 mg; ranges are < 0.3 good, 0.3-0.5 acceptable, 0.5-1.0 marginal, 1.0+ high. Sadly, in the closed office those readings are now approaching 1.1. I'm not too surprised; the house is in renovation and there's a lot of relatively new paint, which I could smell when I moved in, but 3 weeks of open windows and air sponges haven't cleared it. Maybe I should crank up the heat to try to 'cook off' the house. I could also add a carbon filter to the purifier setup... CO2 is rising too, 700.

Well, I got the VOC ranges off a couple web sites; the monitor itself calls it "slightly high" at the moment, with a yellow color code. I should probably open the windows, outdoor PM is pretty low anyway. VOC rose to 1.22 while I was writing all this.

Anyway, I can give both the QingPing and the DIY purifier cautious recommendations.

Though the wifi part of the QingPing is a bit laughable; it thinks I'm in Santa Clara, not Albany. It also thought the UV index was 6 at 15:45 in late October, when my weather sites don't put UV above 4 even at 1 pm, solar noon.

Edit:

Cooking! Boiled pasta, and pan-fried two strips of bacon. Probably the latter is the culprit, but PM shot as high as 96 mcg, and CO2 1400+. This with two mildly open windows and huge interior space past one doorway. Slow to come down, too. And that's not the sensor, because when I brought it back to the office, PM quickly dropped to 5.

Outside, VOC quickly went down to 0.02 or lower, as one would hope.

Edit: tweet and photos of my air purifier. https://twitter.com/mindstalk/status/1584776040333086721