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I am living in an area with periodic very high air pollution. So opening the windows to bring CO2 down will bring in fine dust pollution. I retrofitted my hous

I am living in an area with periodic very high air pollution. So opening the windows to bring CO2 down will bring in fine dust pollution. I retrofitted my house with a demand controlled fresh air ventilation system that takes outside air runs it through a set of high performance filters and pushes it into the house. I can consistently keep PM2.5 levels at zero and CO2 below 600ppm. I wrote an article about it [1] including detailed charts about CO2 build up. [1] https://www.airgradient.com/open-airgradient/blog/positive-pressure-systems-for-clean-air/ https://www.airgradient.com/open-airgradient/blog/positive-p...

cactusplant7374 4y ago
That is truly awesome. How much did you spend?
- ahaucnx 4y ago
  There was quite some work involved because the house was originally very leaky and for this system to work it needs a very good sealed home. So I spent quite some time and money to close the leaks. It probably cost me a few thousand USD to get it to this point but for us it was definitely worth it. Especially because we periodically have extremely high outdoor air pollution.
  - cactusplant7374 4y ago
    Does the few thousand include the blowers?
    - ahaucnx 4y ago
      Yes but it was a very customized solution which we also used to test and improve our air quality monitors that we develop.
  - technological 4y ago
    How did you find the leaks ?
    - zdragnar 4y ago
      If there is a thermal difference (cold outside and furnace is running, or hot and AC is running) a cheap thermal camera can find them fairly quickly. In the US at least, where building codes favor air sealed construction, door blower tests are fairly accessible: https://www.energy.gov/energysaver/blower-door-tests https://www.energy.gov/energysaver/blower-door-tests
      - kolinko 4y ago
        How did you use the thermal camera exactly? Any tutorials on that? I have a garage, and I had issues with using the thermal camera - if the building materials were not uniform they reflected/radiated IR unevenly. It could show a piece of uninsulated area as hot and very well insulated as cold.
        namibj 4y ago
        Get some wash-off spray-on chalk (essentially spraypaint that won't survive the next rain, because it's made to disappear when hit with rain/a hose). That should give you sufficiently uniform surface emmissivity to deal with those problem spots.
        kolinko 4y ago
        Thanks! Do I do the measurements from the outside then, not the inside? Seems difficult in some cases unless I have a drone (roof, other hard to reach areas). Do you know if i can find a tutorial anywhere? I tried googling, but couldn't find anything easy to understand.
    - IanOzsvald 4y ago
      I use a FLIR One on Android. I've charted internal leaks (where cold air blows in through cracks) and external (where heat escapes through eg old windows). Wait for a cold day (eg 0C), heat the house, investigate everything you can. My 1930s London house has SO many leaks, I've spent 3 years slowly fixing them. I have a talk I should give on using 12 Govee hygrometers to back-calculate moisture (absolute humidity) coherent per room, as I was charting moisture loss to trace air leaks.
kerpotgh 4y ago
I don’t like it. That’s how you end up with kids that are allergic to everything and have weak immune systems overall. I understand the CO2 control but let the dust and pollen flow!
- ahaucnx 4y ago
  Not sure if you are sarcastic or not but the place I live has at times air quality classified as "Hazardous" and then hospitals are full of people having problems to breathe. If you are concerned about the zero pm 2.5 environment, studies show negative health impacts from pm2.5 even on very low concentrations and the WHO just last year lowered their guideline levels to only 5 ug/m3 pm2.5.
  - Dalewyn 4y ago
    I recall that allergies to some degree are caused by too little or too much immune system stimuli early in life. Remember that allergies are a malfunctioning of the immune system, treating non-hazardous things as hazardous and causing unnecessary inflamations. It's obviously better to breathe clean air than dirty air, but there is a point to be had that being in a "too clean" or "too dirty" environment when your immune system is still calibrating itself could have long-term negative consequences.
    - travisjungroth 4y ago
      It's not one spectrum from "too clean" to "too dirty". It's at the very least two. For example, let's say pollen and coal. What you're talking about, having allergy issues from too little exposure, applies to pollen. Let's call those "adaptive particles" (term I just made up). What you're talking about does not apply to coal. The ideal amount of coal particles in your lungs is zero. There is no age where it helps to get exposed, no allergy to avoid getting. Let's call these "non-adaptive particles". If you live in a city, it's very likely that the negative impact from these non-adaptive is way worse than the negative impact of missing out on the adaptive particles. Breathing the air, you're increasing your risk of asthma a lot to decrease your chance of allergies a bit.
kayson 4y ago
Can you elaborate on "Standalone air purifiers work but they quickly lead to high CO2 concentrations inside rooms t"? How do air purifiers increase co2...?
- ravel-bar-foo 4y ago
  My guess would be that in order for a standalone air purifier to work one has to limit the ventilation, which quickly leads to high CO2 concentrations in small urban flats.
  - ahaucnx 4y ago
    Yes correct. The CO2 increases by humans and air purifiers do not remove CO2 or bring in fresh air. To have the air purifier work effectively you need to keep your windows and doors closed.
    - robga 4y ago
      > To have the air purifier work effectively you need to keep your windows and doors closed. Isn’t it the case that you can open windows to the extent that the air purifier CADR can cope with the influx? Then they are still “effective”. The relative air quality inside and outside is also highly relevant. I say this as someone with AGs, since I frequently do this dance when CO2 rises.
      - ahaucnx 4y ago
        It really depends on the outside pollution levels. In our experience indoor purification reduction with air purifiers correlate with outdoor pollution levels. So if it's really bad outside opening the windows just a little bit will already let a lit of dirty air on with which the purifier might not be able to effectively cope with.
      - 5e92cb50239222b 4y ago
        If your outside air is clean enough that you can afford to open a window with a purifier running, you probably don't need the purifier. I have two Xiaomi ones running 24/7, with CADR 300-350 on both. In colder months (which are 7-8 per year) they're running at maximum speed for most of the time (~2300-2400 RPM). Every window and door is shut, all gaps are plugged with expanding foam. Even with all that, the indoor PM2.5 almost never goes below 2-5 µg/m³, with jumps up to 30-40 µg/m³ when it's really bad outside. Opening a window even for a few millimeters is enough for PM 2.5 to go to a significant portion of what's happening outside (which is almost always hundreds of micrograms, sometimes thousands), and no purifier can beat that. Maybe if I put ten of them in a row, but it's expensive and noise will be unbearable.
hackerlight 4y ago
How much does the electricity cost to run it per annum?
EVa5I7bHFq9mnYK 4y ago
I have such system running 24/7 for 5 years now in my apartment. It costs $20/month in the winter because it needs to heat the freezing air coming in. There is also noticable noise if I am doing physical activity and it needs to blow the CO2 out more quickly.
- _Microft 4y ago
  Maybe you could add a heat exchanger to the system to recover some of the heat?
  - MengerSponge 4y ago
    There are commercially produced systems to do this. They're called ERV or HRV: ERV: Energy Recovery Ventilation eg: https://ephoca.com/aio-wall-mounted-pro/ https://ephoca.com/aio-wall-mounted-pro/ An example of a less expensive module sized for a whole home: Panasonic intellibalance https://na.panasonic.com/us/home-and-building-solutions/ventilation-indoor-air-quality/energy-recovery-ventilators/intelli-balancetm-100-balanced-air-solution-cold-climate-erv-50-100-cfm https://na.panasonic.com/us/home-and-building-solutions/vent...
  - EVa5I7bHFq9mnYK 4y ago
    I did the calculation, at that rate that investment will never pay off. Besides, I find it hard to believe compact heat exchangers can exchange meaningful amount of heat at 40 m3/hr flow rate.
    - jaggederest 4y ago
      They can't, but you don't run them constantly at a low rate. They cycle on and off to hit your targeted air exchange rate. That would be about a 50% duty cycle on low, so like 15 minutes on, 15 minutes off, constantly. They're definitely not "free", but they do return a lot of the heat you're using. 90% or so is pretty standard.
      - EVa5I7bHFq9mnYK 4y ago
Gordonjcp 4y ago
Why are you going to all that effort? "Poor air quality" isn't going to kill you. You are going to die of heart failure, or in a road accident. Way way way behind that you're going to die of cancer, and about twice as far behind that are a bunch of other non-preventable diseases. Stop buying toys and fix the big problem first.
- 5e92cb50239222b 4y ago
  Others just keep downvoting this comment, I'll offer a counterpoint instead. I live in a city with air pollution levels that are considered extreme by Western standards (which I've checked and compared multiple times). Frequent SO₂ spikes up to 10 milligrams/m³ (and sometimes even more); NO₂ at 150-200 µg/m³ or higher; yearly PM2.5 averages of 200+ µg/m³, and so on. Respiratory illness rates are 4× compared to national average. Life expectancy is lower by about 5-8 years. If you look at this page, in most the world CVD beats cancers by about 2:1. Over here the ratio is much closer to 1:1. https://en.wikipedia.org/wiki/List_of_causes_of_death_by_rate https://en.wikipedia.org/wiki/List_of_causes_of_death_by_rat... Everyone knows that air pollution is to blame, including the government, but they have shinier things to spend money on.
  - Gordonjcp 4y ago
    And you are still going to be killed in traffic way way way before air pollution gets you.
    - flangola7 4y ago
      That's not what those cancer rates suggest. Either way, I'm not sure what the relevance of motor vehicle deaths is, just because I might die in a car accident doesn't mean I don't exercise and eat heathy to avoid having a heart attack.
    - 5e92cb50239222b 4y ago
      Well, let's hope so, because currently I am at full speed towards developing COPD (despite never having smoked) and personally know way more cancer victims than victims of traffic accidents.
flippinburgers 4y ago
Where does one get such a system (the ventilation system)? What are general costs?
- lathiat 4y ago
  Search “energy recovery ventilation” (ERV) or Heat Recovery Ventilation (HRV) Great introduction here: https://renew.org.au/renew-magazine/efficient-homes/mechanical-ventilation-with-heat-recovery-fresh-air-without-the-heat-loss-or-gain/ https://renew.org.au/renew-magazine/efficient-homes/mechanic...
- _spduchamp 4y ago
  I built a well insulated 9'x12' shed in my backyard to use as a workshop and for growing sprouts and seedlings. I installed a Cyclone Dual Air Single Room High-Efficiency Energy Recovery Ventilator from Home Depot. That unit was about $1000. It works quite well and my shed is super comfortable to work in year round. I installed a larger ERV (about $2000) that is tied into our house central air. It has been a huge improvement to the comfort in the house.

cactusplant7374 4y ago

That is truly awesome. How much did you spend?

ahaucnx 4y ago
There was quite some work involved because the house was originally very leaky and for this system to work it needs a very good sealed home. So I spent quite some time and money to close the leaks. It probably cost me a few thousand USD to get it to this point but for us it was definitely worth it. Especially because we periodically have extremely high outdoor air pollution.
- cactusplant7374 4y ago
  Does the few thousand include the blowers?
  - ahaucnx 4y ago
    Yes but it was a very customized solution which we also used to test and improve our air quality monitors that we develop.
- technological 4y ago
  How did you find the leaks ?
  - zdragnar 4y ago
    If there is a thermal difference (cold outside and furnace is running, or hot and AC is running) a cheap thermal camera can find them fairly quickly. In the US at least, where building codes favor air sealed construction, door blower tests are fairly accessible: https://www.energy.gov/energysaver/blower-door-tests https://www.energy.gov/energysaver/blower-door-tests
    - kolinko 4y ago
      How did you use the thermal camera exactly? Any tutorials on that? I have a garage, and I had issues with using the thermal camera - if the building materials were not uniform they reflected/radiated IR unevenly. It could show a piece of uninsulated area as hot and very well insulated as cold.
      - namibj 4y ago
        Get some wash-off spray-on chalk (essentially spraypaint that won't survive the next rain, because it's made to disappear when hit with rain/a hose). That should give you sufficiently uniform surface emmissivity to deal with those problem spots.
        kolinko 4y ago
        Thanks! Do I do the measurements from the outside then, not the inside? Seems difficult in some cases unless I have a drone (roof, other hard to reach areas). Do you know if i can find a tutorial anywhere? I tried googling, but couldn't find anything easy to understand.
  - IanOzsvald 4y ago
    I use a FLIR One on Android. I've charted internal leaks (where cold air blows in through cracks) and external (where heat escapes through eg old windows). Wait for a cold day (eg 0C), heat the house, investigate everything you can. My 1930s London house has SO many leaks, I've spent 3 years slowly fixing them. I have a talk I should give on using 12 Govee hygrometers to back-calculate moisture (absolute humidity) coherent per room, as I was charting moisture loss to trace air leaks.

kerpotgh 4y ago

I don’t like it. That’s how you end up with kids that are allergic to everything and have weak immune systems overall. I understand the CO2 control but let the dust and pollen flow!

ahaucnx 4y ago
Not sure if you are sarcastic or not but the place I live has at times air quality classified as "Hazardous" and then hospitals are full of people having problems to breathe. If you are concerned about the zero pm 2.5 environment, studies show negative health impacts from pm2.5 even on very low concentrations and the WHO just last year lowered their guideline levels to only 5 ug/m3 pm2.5.
- Dalewyn 4y ago
  I recall that allergies to some degree are caused by too little or too much immune system stimuli early in life. Remember that allergies are a malfunctioning of the immune system, treating non-hazardous things as hazardous and causing unnecessary inflamations. It's obviously better to breathe clean air than dirty air, but there is a point to be had that being in a "too clean" or "too dirty" environment when your immune system is still calibrating itself could have long-term negative consequences.
  - travisjungroth 4y ago
    It's not one spectrum from "too clean" to "too dirty". It's at the very least two. For example, let's say pollen and coal. What you're talking about, having allergy issues from too little exposure, applies to pollen. Let's call those "adaptive particles" (term I just made up). What you're talking about does not apply to coal. The ideal amount of coal particles in your lungs is zero. There is no age where it helps to get exposed, no allergy to avoid getting. Let's call these "non-adaptive particles". If you live in a city, it's very likely that the negative impact from these non-adaptive is way worse than the negative impact of missing out on the adaptive particles. Breathing the air, you're increasing your risk of asthma a lot to decrease your chance of allergies a bit.

kayson 4y ago

Can you elaborate on "Standalone air purifiers work but they quickly lead to high CO2 concentrations inside rooms t"? How do air purifiers increase co2...?

ravel-bar-foo 4y ago
My guess would be that in order for a standalone air purifier to work one has to limit the ventilation, which quickly leads to high CO2 concentrations in small urban flats.
- ahaucnx 4y ago
  Yes correct. The CO2 increases by humans and air purifiers do not remove CO2 or bring in fresh air. To have the air purifier work effectively you need to keep your windows and doors closed.
  - robga 4y ago
    > To have the air purifier work effectively you need to keep your windows and doors closed. Isn’t it the case that you can open windows to the extent that the air purifier CADR can cope with the influx? Then they are still “effective”. The relative air quality inside and outside is also highly relevant. I say this as someone with AGs, since I frequently do this dance when CO2 rises.
    - ahaucnx 4y ago
      It really depends on the outside pollution levels. In our experience indoor purification reduction with air purifiers correlate with outdoor pollution levels. So if it's really bad outside opening the windows just a little bit will already let a lit of dirty air on with which the purifier might not be able to effectively cope with.
    - 5e92cb50239222b 4y ago
      If your outside air is clean enough that you can afford to open a window with a purifier running, you probably don't need the purifier. I have two Xiaomi ones running 24/7, with CADR 300-350 on both. In colder months (which are 7-8 per year) they're running at maximum speed for most of the time (~2300-2400 RPM). Every window and door is shut, all gaps are plugged with expanding foam. Even with all that, the indoor PM2.5 almost never goes below 2-5 µg/m³, with jumps up to 30-40 µg/m³ when it's really bad outside. Opening a window even for a few millimeters is enough for PM 2.5 to go to a significant portion of what's happening outside (which is almost always hundreds of micrograms, sometimes thousands), and no purifier can beat that. Maybe if I put ten of them in a row, but it's expensive and noise will be unbearable.

hackerlight 4y ago

How much does the electricity cost to run it per annum?

EVa5I7bHFq9mnYK 4y ago

I have such system running 24/7 for 5 years now in my apartment. It costs $20/month in the winter because it needs to heat the freezing air coming in. There is also noticable noise if I am doing physical activity and it needs to blow the CO2 out more quickly.

_Microft 4y ago
Maybe you could add a heat exchanger to the system to recover some of the heat?
- MengerSponge 4y ago
  There are commercially produced systems to do this. They're called ERV or HRV: ERV: Energy Recovery Ventilation eg: https://ephoca.com/aio-wall-mounted-pro/ https://ephoca.com/aio-wall-mounted-pro/ An example of a less expensive module sized for a whole home: Panasonic intellibalance https://na.panasonic.com/us/home-and-building-solutions/ventilation-indoor-air-quality/energy-recovery-ventilators/intelli-balancetm-100-balanced-air-solution-cold-climate-erv-50-100-cfm https://na.panasonic.com/us/home-and-building-solutions/vent...
- EVa5I7bHFq9mnYK 4y ago
  I did the calculation, at that rate that investment will never pay off. Besides, I find it hard to believe compact heat exchangers can exchange meaningful amount of heat at 40 m3/hr flow rate.
  - jaggederest 4y ago
    They can't, but you don't run them constantly at a low rate. They cycle on and off to hit your targeted air exchange rate. That would be about a 50% duty cycle on low, so like 15 minutes on, 15 minutes off, constantly. They're definitely not "free", but they do return a lot of the heat you're using. 90% or so is pretty standard.
    - EVa5I7bHFq9mnYK 4y ago

Gordonjcp 4y ago

Why are you going to all that effort? "Poor air quality" isn't going to kill you. You are going to die of heart failure, or in a road accident. Way way way behind that you're going to die of cancer, and about twice as far behind that are a bunch of other non-preventable diseases. Stop buying toys and fix the big problem first.

5e92cb50239222b 4y ago
Others just keep downvoting this comment, I'll offer a counterpoint instead. I live in a city with air pollution levels that are considered extreme by Western standards (which I've checked and compared multiple times). Frequent SO₂ spikes up to 10 milligrams/m³ (and sometimes even more); NO₂ at 150-200 µg/m³ or higher; yearly PM2.5 averages of 200+ µg/m³, and so on. Respiratory illness rates are 4× compared to national average. Life expectancy is lower by about 5-8 years. If you look at this page, in most the world CVD beats cancers by about 2:1. Over here the ratio is much closer to 1:1. https://en.wikipedia.org/wiki/List_of_causes_of_death_by_rate https://en.wikipedia.org/wiki/List_of_causes_of_death_by_rat... Everyone knows that air pollution is to blame, including the government, but they have shinier things to spend money on.
- Gordonjcp 4y ago
  And you are still going to be killed in traffic way way way before air pollution gets you.
  - flangola7 4y ago
    That's not what those cancer rates suggest. Either way, I'm not sure what the relevance of motor vehicle deaths is, just because I might die in a car accident doesn't mean I don't exercise and eat heathy to avoid having a heart attack.
  - 5e92cb50239222b 4y ago
    Well, let's hope so, because currently I am at full speed towards developing COPD (despite never having smoked) and personally know way more cancer victims than victims of traffic accidents.

flippinburgers 4y ago

Where does one get such a system (the ventilation system)? What are general costs?

lathiat 4y ago
Search “energy recovery ventilation” (ERV) or Heat Recovery Ventilation (HRV) Great introduction here: https://renew.org.au/renew-magazine/efficient-homes/mechanical-ventilation-with-heat-recovery-fresh-air-without-the-heat-loss-or-gain/ https://renew.org.au/renew-magazine/efficient-homes/mechanic...
_spduchamp 4y ago
I built a well insulated 9'x12' shed in my backyard to use as a workshop and for growing sprouts and seedlings. I installed a Cyclone Dual Air Single Room High-Efficiency Energy Recovery Ventilator from Home Depot. That unit was about $1000. It works quite well and my shed is super comfortable to work in year round. I installed a larger ERV (about $2000) that is tied into our house central air. It has been a huge improvement to the comfort in the house.