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First clean water, now clean air

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Re: First clean water, now clean air

#61

Post by blkhawk »

bsenftner wrote: post #23
isp wrote: post #4

Earlier quoted context omitted.

> So if we want to do something, I think the first step is really to get visibility to the problem A sensible first step would be to very visibly display CO₂ monitors in buildings (e.g., throughout office buildings, schools, etc) Once the CO₂ levels become visible, this in itself creates an incentive to improve. Related from UK (2021): "All schools to receive carbon dioxide monitors" - https://www.gov.uk/government/n…

In Japan, it is common to see CO₂ monitor displays outside contained meeting spaces, such as theaters. My wife purchased an Aronet CO₂ monitor, and I took it with me on a business trip last week. The CO₂ while on the flight was in the 3000's range. The CO₂ at my client's office was in the mid 2000's range, as well as the hotel. Opening the hotel window the allowed 2 inches reduces CO₂ to the 600 range in 10 minutes,…

I have had a self-build CO2 monitor for several years now and I find the airplane example Surprising.

AFAIK the air in a Plane is cycled out too fast for that amount to develop. Maybe the Lower air pressure was the cause? Since it was portable it was probably the NIR type? If its not measuring all the time it might also be the heater type - I am really not sure how that type would deal with low pressure. Or was is the "eCO2" type - in that case well I doubt you get anything out of that thing in a plane except a high number.

One thing I noticed is that CO2 seems to "flow and pool" in certain places as it seemingly "rains" down and the room is "filled" from the bottom up. A Table for instance might develop a layer that is thick enough for my meter to hoover it up (it has a fan).

Re: First clean water, now clean air

#62

Post by throw0101a »

miduil wrote: post #10
throw0101b wrote: post #5

> Ultraviolet germicidal irradiation (UVGI) Please do not do/use this. Generally anything that is 'active', like UV lamps or ozone emitters, is not a good idea: * https://www.youtube.com/watch?v=hSFQQpgvgeo&t=6m1s * Interviewee: https://civmin.utoronto.ca/home/about-us/directory/professor... All that's needed for good indoor air quality (IAQ) is an ERV/HRV which exhausts stale indoor air and brings in fresh outdoor a…

I share their sentiment, especially because they are trying to explain the topic for the novice buyer - but I think it oversimplifies the issue and the discussion/benefit of UVGI. UVGI does not create Ozone, some companies even sell certified lamps that will definitively not go into the UV spectrum that can cause Ozone. This is true for UV-C and in the postings mention of new far-UVC LEDs. https://www.uvresources.com…

> I share their sentiment, especially because they are trying to explain the topic for the novice buyer - but I think it oversimplifies the issue and the discussion/benefit of UVGI.

Most people probably don't change their air filters often enough at home: I have zero confidence of them maintaining an UVGI (themselves, or wanting to shell out the cash for someone to come in).

The best thing to do is circulate air per ASHRAE-recommendations and get high-MERV filters (and hope they are swapped regularly).

Re: First clean water, now clean air

#63

Post by sergioisidoro »

clairity wrote: post #47
sergioisidoro wrote: post #2

I bought a CO2 monitor, and although the effects of CO2 in cognition and energy levels are debatable[1], it shocked me and raised awareness to how poor my indoor ventilation is. We live in a small apartment, and just being 30 min with 2 people in the room raises the CO2 ppm from 400 to >1000. Opening a window quickly lowers it. Never-mind doing some light activity like yoga or similar. So if we want to do something,…

> "although the effects of CO2 in cognition and energy levels are debatable" it's really not debatable. the feeling of stuffiness is a function of many things, but environmentally, it's mostly temperature and humidity (we humans are hot and breathe out lots of humidity). there are no cognitive/energy effects until you get into the 10's of thousand of ppm, as the mechanism of action is competing out oxygen, not some i…

Yes they are debatable. There are cognitive performance tests that show statistically significant decline in many tasks above 1500ppm, especially on planning tasks. That's independently of the feeling of "stuffiness".

If these measurable declines have a sufficient impact on our lives and productivity is the debatable part.

Edit: here's one reference: "We also found effects of CO2 (a proxy for ventilation) on cognitive function. For every 500ppm increase, we saw response times 1.4-1.8% slower, and 2.1-2.4% lower throughput"

https://www.hsph.harvard.edu/healthybuildings/2021/09/09/imp...

Re: First clean water, now clean air

#64

Post by sergioisidoro »

za3faran wrote: post #34
sergioisidoro wrote: post #2

I bought a CO2 monitor, and although the effects of CO2 in cognition and energy levels are debatable[1], it shocked me and raised awareness to how poor my indoor ventilation is. We live in a small apartment, and just being 30 min with 2 people in the room raises the CO2 ppm from 400 to >1000. Opening a window quickly lowers it. Never-mind doing some light activity like yoga or similar. So if we want to do something,…

Which monitor manufacturer are you using?

I bought mine from a construction material supply web store, and was looking for one of the cheaper ones. Its a Trotec. I wouldn't trust the absolute values so much, but i believe it's directionally correct.

Re: First clean water, now clean air

#65

Post by schiffern »

throw0101a wrote: post #59
mensetmanusman wrote: post #32

Earlier quoted context omitted.

UV is more than UV, there is UVA UVB UVC, etc. Some UVC generates Ozone, some do not. Wavelength and spectral Q factor matter. It’s possible to have a UV system that does what you want without the downside, but it does cost.

> It’s possible to have a UV system that does what you want without the downside, but it does cost. The main downside is that you are introducing a chemistry experiment into your ventilation system. If you want clean air, then (a) cycle in/outside air at ASHRAE-recommended volumes, and (b) use high-MERV/HEPA filters. In wildfire zones and in wildfire season you can perhaps add charcoal filters—if your system is desig…

What I really want is a system that has

• Positive pressure maintenance, so that any air leak paths are not introducing outside air pollutants

• HEPA filtration, using two filters in series so I can "cycle through" filters, moving the post-filter to the pre-filter location and using a brand-new post-filter (this is similar to the ISS water filter change procedure, and maximizes expendable filter utilization); by the series-parallel circuit math, this should requires four times the total area of HEPA filter

• pressure drop sensors, so I only need to replace the HEPA filter when necessary

• activated carbon post-filter that lets me to replace only the granules themselves, using bulk activated carbon

• washable screen prefilter, to avoid premature saturation of the HEPA medium with >10 micron particles

• washable electrostatic prefilter, to avoid premature saturation of the HEPA medium with • HRV/ERV, to avoid unwanted heat and humidity transfer to the outside air

• HRS/ERV Bypass, so I can use "free cooling" / "free heating" to exploit natural temperature differences over the day

• (optional) MERV-13 post-prefilter, to intercept ~95% of PM2.5 and greatly extend the life of the HEPA filter train

Does anyone know of a system that has all these features?

Re: First clean water, now clean air

#66

Post by marcosdumay »

giraffe_lady wrote: post #42
bsenftner wrote: post #23

Earlier quoted context omitted.

In Japan, it is common to see CO₂ monitor displays outside contained meeting spaces, such as theaters. My wife purchased an Aronet CO₂ monitor, and I took it with me on a business trip last week. The CO₂ while on the flight was in the 3000's range. The CO₂ at my client's office was in the mid 2000's range, as well as the hotel. Opening the hotel window the allowed 2 inches reduces CO₂ to the 600 range in 10 minutes,…

No, there won't be any battle. If there were going to it would have been during covid, with improved indoor ventilation being one of the major components of an in-depth mitigation strategy. There was no meaningful attempt or debate about changing ventilation standards then when it would have tangibly saved lives, there certainly won't be now.

The covid years were crazy. People kept cleaning everything with all kinds of poison (thank god somebody published early that alcohol at 70% is enough, otherwise I think we would see people dropping dead from too much poison), that was known to be useless by around April 2020, and yet everybody actively refused to talk about indoor ventilation.

And most were the same people repeating the "are you for or against science?" line.

Crazy years, dominated by completely random propaganda. Discussions on calmer times follow different rules, and if nobody decides to spend a lot of money stopping it, it can follow rational, evidence based lines.

Re: First clean water, now clean air

#67

Post by danans »

> An aside: ventilation plus filtration is the major reason that the risk of Covid infections on flights was and is so relatively low: air in the cabin is replaced every couple minutes, fresh air is drawn from outside the plane, and mixed with recycled air passed through HEPA filters.

IME, the most effective thing to do in a house is filtration inline with the intake of a ventilation system.

In my case, I have an activated carbon and a MERV13 filter that cleans incoming outdoor air just before it's fed to the heat recovery and distribution system.

You still need a separate recirculating filtration system to deal with particulates generated within a house.

Re: First clean water, now clean air

#68

Post by scythe »

throw0101a wrote: post #62
miduil wrote: post #10

Earlier quoted context omitted.

I share their sentiment, especially because they are trying to explain the topic for the novice buyer - but I think it oversimplifies the issue and the discussion/benefit of UVGI. UVGI does not create Ozone, some companies even sell certified lamps that will definitively not go into the UV spectrum that can cause Ozone. This is true for UV-C and in the postings mention of new far-UVC LEDs. https://www.uvresources.com…

> I share their sentiment, especially because they are trying to explain the topic for the novice buyer - but I think it oversimplifies the issue and the discussion/benefit of UVGI. Most people probably don't change their air filters often enough at home: I have zero confidence of them maintaining an UVGI (themselves, or wanting to shell out the cash for someone to come in). The best thing to do is circulate air per…

I work in medical physics. The issue of ozone generation from ionizing radiation has come up from time to time. In radio/fluoro rooms, it's basically undetectable. In radiotherapy, it might reach the odor threshold after long treatments, but this is rare.

These are systems that produce radiation way beyond the energies that can create ozone via UVC. The ozone level is barely measurable and not considered a serious risk. In the video you linked, the narrator opens by saying that ozone barely even makes it through the ventilation system, which is consistent with my understanding of ozone: a reactive, unstable gas. And Dr. Siegel emphasizes this as well: O3 doesn't stick around easily. He doesn't seem to share the presenter's obsession with ozone.

Frankly, I found the video tedious and gave up after a minute. Also, the Siegel's background is mechanical engineering, and he's obviously hedging his statements. Here's an actual scientific review of O3 generation by lamps:

https://onlinelibrary.wiley.com/doi/full/10.1111/php.13391

Critical quote: "Again, soft glass UV-C lamps cannot generate ozone".

>I have zero confidence of them maintaining an UVGI

An unmaintained mercury-vapor lamp will not suddenly violate the laws of physics by emitting radiation below the 254 nm spectral line of mercury. The only mechanism that would alter the ozone generation rate is electrical arcing outside the device, which is really a concern with any electrical equipment and not specific to Hg lamps.

Frankly, most of your posts on this sound like you watch too many videos and don't read enough. "Performing chemistry experiments on yourself" — really? This stuff has been studied for centuries.

A more realistic concern with UVGI is that they don't kill everything and can't replace other ventilation components. Some microbes are very, very radioresistant and you're just not going to deliver 10 kilogray in a continuous flow duct using reasonable levels of power.

Re: First clean water, now clean air

#69

Post by ProZsolt »

mypastself wrote: post #3
sergioisidoro wrote: post #2

I bought a CO2 monitor, and although the effects of CO2 in cognition and energy levels are debatable[1], it shocked me and raised awareness to how poor my indoor ventilation is. We live in a small apartment, and just being 30 min with 2 people in the room raises the CO2 ppm from 400 to >1000. Opening a window quickly lowers it. Never-mind doing some light activity like yoga or similar. So if we want to do something,…

Not to hijack your thread, but I wonder if anyone here’s built their own Raspberry/Arduino CO2 monitor? Which (reliable) sensors did you use? Did you find it more affordable than purchasing a monitor, especially if you already had unused microcontrollers lying around the house?

I'm currently developing my own monitor based on Sensirion SCD40(CO2/temperature/humidity) and Plantower PMS7003(PM2.5). The SCD40 is lot smaller than any NDIR sensor, but with the same accuracy[1].

My goal is to get a cheap (~$50) sensor in a small package that I can put in every room in my house. It will be modular so I skip the display and the PM2.5 sensor and it can be cheap as ~$25

[1]: https://www.airgradient.com/open-airgradient/blog/co2-sensor...

Re: First clean water, now clean air

#70

Post by schiffern »

bsenftner wrote: post #56
hammock wrote: post #46

Earlier quoted context omitted.

When driving, does running the air (not on recirc) not exchange enough air?

Opening a car window or running air not on recirc immediately drops the readings to safe levels. I also noticed when in the Uber returning from the airport, the air was in the high 3000's and I explained to the driver, he opened all the windows and I think I scared him a bit.

Note that, to minimize pollution from vehicle exhaust, you want to set your air to "recirculate". Unsurprisingly, the roadway is where vehicle pollution is most concentrated!

https://www.latimes.com/science/sciencenow/la-xpm-2013-sep-1...

Usually what I do is set it on recirculate, and then every ~10 minutes I periodically "flush" the CO2-laden interior air for a minute or so. Ideally, I'm able to do this "flush" when I'm away from a major city or high-traffic road (and not when driving behind a soot-spewing diesel bus/semi/garbage/cement truck).

I wish there were some way to automate this logic!

---

(and yes, my dear observant reader, if I could recirculate "only" 90% of the exterior air it would achieve the same steady-state result, but modern cars got rid of the "slider" that lets you select a percentage of recirculate air... ::sigh::)

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