3 ms·

At the point where you spend >$400 you might as well buy hardware to purify the air... Unless you have a very specific molecule in mind, a standard HEPA + carbo

At the point where you spend >$400 you might as well buy hardware to purify the air... Unless you have a very specific molecule in mind, a standard HEPA + carbon filter will fix 99% of your problem.

stephen_g 3y ago
Usually yes. But it does depend on the air quality outside and how leaky the building is - in certain places with very poor air quality you'd need a very serious flow rate through your purifier to keep up unless you have a positive pressure system (where you filter the air coming in to the building instead of just recirculating through a filter), and keep it at a positive pressure to stop dirty air constantly leaking in (especially when running bathroom exhaust fans or kitchen rangehoods that vent outside). In fact there's an article on the very same blog as the original post about it - https://www.airgradient.com/blog/positive-pressure-systems-for-clean-air/ https://www.airgradient.com/blog/positive-pressure-systems-f... Of course the downside is larger load on air conditioning, at which point you can look at heat recovery or energy recovery ventilation systems. I'm quite keen to get one of those to get more fresh air in since I can't leave my front or most of the side windows of the house open at night (road gets too noisy in the morning).
- FabHK 3y ago
  Exactly. It's fairly straightforward to get PM2.5 down while CO2 goes up, and vice versa. The trick is to control both.
Retric 3y ago
Smoke (aka fire), Humidity, and Carbon monoxide are worth monitoring and aren’t going to be fixed by a HEPA and carbon filter. Further if you’re concerned about regular air pollution it’s worth verifying how well your filtration is working.
- aidenn0 3y ago
  Smoke is a combination of particulates and VOCs which will respectively be filtered by HEPA and carbon filters.
  - ahaucnx 3y ago
    Carbon filters typically do not last very long so it's good to monitor TVOCs.
    - aidenn0 3y ago
      Oh, absolutely; I was just responding to the claim that smoke isn't filterable. If you have an intentional fire, you can maintain your filters and run them; spot checking particulates and VOCs. If you are worried about unintentional fires, you address that with a $40 smoke alarm, not a $6k AQM.
      - Retric 3y ago
        You missed the point. Smoke from a burning couch isn’t the issue, the burning couch is.
        aidenn0 3y ago
        > If you are worried about unintentional fires, you address that with a $40 smoke alarm, not a $6k AQM.
        Retric 3y ago
        Redundancy. Also, 40$ smoke detectors can take a while to alert you to a fire in your basement etc. So it’s often a good idea to have a whole house smoke alarm system.
    - reaperman 3y ago
      These last a long time, FWIW. >1 year at surprisingly high flow rates. https://terra-bloom.com/collections/carbon-filters https://terra-bloom.com/collections/carbon-filters

At the point where you spend >$400 you might as well buy hardware to purify the air... Unless you have a very specific molecule in mind, a standard HEPA + carbon filter will fix 99% of your problem.

stephen_g 3y ago

Usually yes. But it does depend on the air quality outside and how leaky the building is - in certain places with very poor air quality you'd need a very serious flow rate through your purifier to keep up unless you have a positive pressure system (where you filter the air coming in to the building instead of just recirculating through a filter), and keep it at a positive pressure to stop dirty air constantly leaking in (especially when running bathroom exhaust fans or kitchen rangehoods that vent outside). In fact there's an article on the very same blog as the original post about it - https://www.airgradient.com/blog/positive-pressure-systems-for-clean-air/ https://www.airgradient.com/blog/positive-pressure-systems-f... Of course the downside is larger load on air conditioning, at which point you can look at heat recovery or energy recovery ventilation systems. I'm quite keen to get one of those to get more fresh air in since I can't leave my front or most of the side windows of the house open at night (road gets too noisy in the morning).

FabHK 3y ago
Exactly. It's fairly straightforward to get PM2.5 down while CO2 goes up, and vice versa. The trick is to control both.

Retric 3y ago

Smoke (aka fire), Humidity, and Carbon monoxide are worth monitoring and aren’t going to be fixed by a HEPA and carbon filter. Further if you’re concerned about regular air pollution it’s worth verifying how well your filtration is working.

aidenn0 3y ago
Smoke is a combination of particulates and VOCs which will respectively be filtered by HEPA and carbon filters.
- ahaucnx 3y ago
  Carbon filters typically do not last very long so it's good to monitor TVOCs.
  - aidenn0 3y ago
    Oh, absolutely; I was just responding to the claim that smoke isn't filterable. If you have an intentional fire, you can maintain your filters and run them; spot checking particulates and VOCs. If you are worried about unintentional fires, you address that with a $40 smoke alarm, not a $6k AQM.
    - Retric 3y ago
      You missed the point. Smoke from a burning couch isn’t the issue, the burning couch is.
      - aidenn0 3y ago
        > If you are worried about unintentional fires, you address that with a $40 smoke alarm, not a $6k AQM.
        Retric 3y ago
        Redundancy. Also, 40$ smoke detectors can take a while to alert you to a fire in your basement etc. So it’s often a good idea to have a whole house smoke alarm system.
  - reaperman 3y ago
    These last a long time, FWIW. >1 year at surprisingly high flow rates. https://terra-bloom.com/collections/carbon-filters https://terra-bloom.com/collections/carbon-filters