4 ms·

In practice, how does one try to achieve a balance between CO2 and PM? Do you open the windows for a while when CO2 is up and PM is down, and then close them an

by tehnub 5y ago

In practice, how does one try to achieve a balance between CO2 and PM? Do you open the windows for a while when CO2 is up and PM is down, and then close them and run your purifiers when CO2 starts to go back down? Is it possible to keep both low with HEPA filters on the windows?

simondotau 5y ago
The best case solution would be a passive house with MVHR (Mechanical Ventilation with Heat Recovery) and incoming air filtration. This means your home has a steady flow of fresh, low-CO2 air that is filtered for pollen and other particles (depending on the air filter chosen).
- laurent92 5y ago
  This. Architects now include heat exchangers in houses, so air is renewed at basically the same temperature, ensuring ideal comfort for low CO2.
- ahaucnx 5y ago
  Another solution is to install a positive pressure system with high performance HEPA filters. This is especially recommended if you live in areas with very high air pollution. Positive pressure systems can virtually achieve zero AQI inside even on the worst polluted days. You can read more here: [1] https://www.airgradient.com/blog/2020/01/08/positive-pressure-systems-for-clean-air/ https://www.airgradient.com/blog/2020/01/08/positive-pressur... [2] https://seetheair.wordpress.com/2021/04/26/thailand-school-sets-the-aq-bar-high-an-example-to-be-followed/ https://seetheair.wordpress.com/2021/04/26/thailand-school-s...
clairity 5y ago
co2 and pm should both go down with windows open. i put my air purifiers on low when the windows are open to deal with the particles i throw up by moving around and doing stuff indoors. with the windows closed (usually only at night), i put the air purifiers on medium/high.
- blackoil 5y ago
  Don't think this would be true in any city in Asia or for city centers around the world.
  - clairity 5y ago
    i live in LA on a relatively busy neighborhood street and according to my air quality meter, it’s true. concentrations go down during the day (windows open) and up at night (windows closed). edit: i mentioned the road to note that outdoor pollution is higher during the day, yet opening the windows despite that lowers overall particulate levels indoors. it may be different in indian cities or cities like beijing with much higher pollution levels.
- PurpleFoxy 5y ago
  I have noticed every time I open my windows, the no2 levels reported on my Dyson filter spike. Not sure what to make of it but it’s interesting.
  - clairity 5y ago
    nox is a combustion byproduct so probably that?
    - lmm 5y ago
      Yeah I would assume it was coming mostly from nearby cars.
      - PurpleFoxy 5y ago
        The crazy thing is there are no nearby cars. There is a highway about 1.5km away which I assume it must all blow from. There is nothing else within 1.5km
- scaladev 5y ago
  > co2 and pm should both go down with windows open. Very much depends on where you live. I have a few DIY air quality stations with data being piped to Grafana. I just looked at the latest data, the average outside PM level for the past 5 months has been around 100 µg/m³, while inside it's around 10 µg/m³. This spring happens to be pretty windy and this skews the outside levels down, otherwise the ratio would be much worse.
colechristensen 5y ago
I keep my HEPA filters on with the windows always open. If the air quality is decent outside, it is easy to maintain a PM2.5 rating of near <10 like this. In California fire season I have a box fan on high in the window pushing air in (and sealing the areas around the window) through an MPR 2800 furnace filter (which is better than the 99.97% rated hepa filters, would be marked as a ULPA filter I believe in different contexts) with this I can maintain the ~0 PM2.5 rating inside even when the AQI outside is >300 while keeping CO2 in check. It's been quite surprising how easily the CO2 spikes with closed windows and doors in the bedroom with just one person... I essentially always have a window in each room open several inches, cracked isn't enough, usually with at least one fan pushing air through a window.
ahaucnx 5y ago
A solution that one of our customers uses (Prem Tinsulanonda International School) is the installation of a positive pressure system. They are able to achieve near zero AQI in their classrooms when you have more than 300 US AQI outside. You can read more on it on the See the Air Blog: https://seetheair.wordpress.com/2021/04/26/thailand-school-sets-the-aq-bar-high-an-example-to-be-followed/ https://seetheair.wordpress.com/2021/04/26/thailand-school-s...

by tehnub 5y ago

simondotau 5y ago

The best case solution would be a passive house with MVHR (Mechanical Ventilation with Heat Recovery) and incoming air filtration. This means your home has a steady flow of fresh, low-CO2 air that is filtered for pollen and other particles (depending on the air filter chosen).

laurent92 5y ago
This. Architects now include heat exchangers in houses, so air is renewed at basically the same temperature, ensuring ideal comfort for low CO2.
ahaucnx 5y ago
Another solution is to install a positive pressure system with high performance HEPA filters. This is especially recommended if you live in areas with very high air pollution. Positive pressure systems can virtually achieve zero AQI inside even on the worst polluted days. You can read more here: [1] https://www.airgradient.com/blog/2020/01/08/positive-pressure-systems-for-clean-air/ https://www.airgradient.com/blog/2020/01/08/positive-pressur... [2] https://seetheair.wordpress.com/2021/04/26/thailand-school-sets-the-aq-bar-high-an-example-to-be-followed/ https://seetheair.wordpress.com/2021/04/26/thailand-school-s...

clairity 5y ago

co2 and pm should both go down with windows open. i put my air purifiers on low when the windows are open to deal with the particles i throw up by moving around and doing stuff indoors. with the windows closed (usually only at night), i put the air purifiers on medium/high.

blackoil 5y ago
Don't think this would be true in any city in Asia or for city centers around the world.
- clairity 5y ago
  i live in LA on a relatively busy neighborhood street and according to my air quality meter, it’s true. concentrations go down during the day (windows open) and up at night (windows closed). edit: i mentioned the road to note that outdoor pollution is higher during the day, yet opening the windows despite that lowers overall particulate levels indoors. it may be different in indian cities or cities like beijing with much higher pollution levels.
PurpleFoxy 5y ago
I have noticed every time I open my windows, the no2 levels reported on my Dyson filter spike. Not sure what to make of it but it’s interesting.
- clairity 5y ago
  nox is a combustion byproduct so probably that?
  - lmm 5y ago
    Yeah I would assume it was coming mostly from nearby cars.
    - PurpleFoxy 5y ago
      The crazy thing is there are no nearby cars. There is a highway about 1.5km away which I assume it must all blow from. There is nothing else within 1.5km
scaladev 5y ago
> co2 and pm should both go down with windows open. Very much depends on where you live. I have a few DIY air quality stations with data being piped to Grafana. I just looked at the latest data, the average outside PM level for the past 5 months has been around 100 µg/m³, while inside it's around 10 µg/m³. This spring happens to be pretty windy and this skews the outside levels down, otherwise the ratio would be much worse.

colechristensen 5y ago

I keep my HEPA filters on with the windows always open. If the air quality is decent outside, it is easy to maintain a PM2.5 rating of near <10 like this. In California fire season I have a box fan on high in the window pushing air in (and sealing the areas around the window) through an MPR 2800 furnace filter (which is better than the 99.97% rated hepa filters, would be marked as a ULPA filter I believe in different contexts) with this I can maintain the ~0 PM2.5 rating inside even when the AQI outside is >300 while keeping CO2 in check. It's been quite surprising how easily the CO2 spikes with closed windows and doors in the bedroom with just one person... I essentially always have a window in each room open several inches, cracked isn't enough, usually with at least one fan pushing air through a window.

ahaucnx 5y ago

A solution that one of our customers uses (Prem Tinsulanonda International School) is the installation of a positive pressure system. They are able to achieve near zero AQI in their classrooms when you have more than 300 US AQI outside. You can read more on it on the See the Air Blog: https://seetheair.wordpress.com/2021/04/26/thailand-school-sets-the-aq-bar-high-an-example-to-be-followed/ https://seetheair.wordpress.com/2021/04/26/thailand-school-s...