9 ms·

Are diy filters effective at removing smells or only removing the measurable particles?

ethanwillis 6y ago
Not sure, but I know my commercial air filter has an optional activated charcoal filter screen in order to do smell removal. I also know that one trick to remove the smoke smell from a used car is to use an ozone generator in the car.
- culopatin 6y ago
  The problem with ozone generators in cars is that they often react with some plastics and do more harm than good. Unfortunately they are the only way of getting in the nooks and crannies and inside the ac vents to clean mold and that kind of stuff. I’ve had steering wheels turn to gel using ozone and they smell funkier than what was in there.
cyounkins 6y ago
Most things that smell are very very small particles not captured by even HEPA filters and require a different kind of filtration. Most commonly activated carbon is used, either as granule or deposited on fibers.
- rckoepke 6y ago
  HEPA filters are actually more efficient at capturing very very small particles (<0.1 micron) than they are at capturing simply small particles (≈0.3 micron). The tiniest particles are light enough to be captured using electrostatic forces rather than the more typical mechanical filtration that is effective at capturing large particles. More precisely, many odors are not particles at all but rather gases/vapors. Activated charcoal can capture larger organic molecules because it has an incredibly jagged/porous surface - just 100 grams of activated charcoal provides over 1,000,000 square feet of "effective" filtration surface area.
  - cyounkins 6y ago
    Yes, that's true that HEPA is very efficient at particles in the 0.01 to 0.1 micron range. It may also be below that, but I personally haven't seen that data. But because HEPA fails to filter gases/vapors, its performance must fall off before 1 angstrom = 0.0001 micron. > odors are not particles at all but rather gases/vapors I think the confusion comes from people referring to "particulate" as particles of >= 0.01 micron, whereas in physics we say that gases/vapors are also composed of particles. They may be single atoms floating (can't actually come up with an example though) or small molecules like O^2, CO, etc, but I'd still call those particles.
    - ClumsyPilot 6y ago
      > 'but I'd still call those particles' But then in your world there are no such things as gasses? If so, the world uses all usefullness
- xiphias2 6y ago
  I don't know any way to filter NO2 effectively from air, and I have tried practically all commercial air filters with the largest carbon filters on the market. The worst parts of air pollution cannot be filtered out without industrial devices (that are part of the air filteration system) as far as I know.
  - ddeck 6y ago
    NO2 and other acidic gases are typically filtered using activated alumina balls impregnated with an oxidizing agent such as potassium permanganate or sodium permanganate. There are residential air purifiers available that use this in combination with activated carbon for their gas stage.
    - xiphias2 6y ago
      I bought IQAir and tried multiple filters (I think they use potassium permanganate), and I wasn't able to significantly reduce NO2 in my room. 3M masks similarly may work if the toxic gas concentration is far above the high levels, but I couldn't get it from normal/high to low levels. Maybe you are talking about an integrated air filtration system, as I haven't tried that yet (though I'm planning to try it).
Havoc 6y ago
Not really. To remove smells ozone generators are used. That stuff is really dangerous though
- xnyan 6y ago
  This is not correct. Activated carbon is very effective and in wide use for odor removal.
  - hajimemash 6y ago
    This is correct, but this is incorrect.
  - Havoc 6y ago
    >This is not correct. No it's not. That 200 USD fine for smoking in hotel rooms? What do you think happens afterwards? Buy a bunch of activated carbon filters? Or get a professional ozone odor removal provider to roll in their with their gear?
xnyan 6y ago
To echo everyone else, you want activated carbon. Put it in your filter stack behind the other filter and you’re golden.
heavyset_go 6y ago
I lit a candle in a room where I had one running, and the filter darkened pretty quickly. It seemed to have caught some of the smoke particles, which can be pretty small at under a micron.
Traubenfuchs 6y ago
Smells are usually VOCs (volatile organic compound). Those need to be trapped in an active carbon filter. An alternative is to destroy them with ozone (also called "activated air", "ionized air"), but to do so one needs ozone concentrations that are unhealthy for living beings. Ozone is very unhealthy! Ozone is generated electrically or via UVC lamps. An especially common and harmful VOC, formaldehyde, can be destroyed by the extremely overpriced dyson air filters via their cryptomic technology.

Not sure, but I know my commercial air filter has an optional activated charcoal filter screen in order to do smell removal. I also know that one trick to remove the smoke smell from a used car is to use an ozone generator in the car.

culopatin 6y ago
The problem with ozone generators in cars is that they often react with some plastics and do more harm than good. Unfortunately they are the only way of getting in the nooks and crannies and inside the ac vents to clean mold and that kind of stuff. I’ve had steering wheels turn to gel using ozone and they smell funkier than what was in there.

cyounkins 6y ago

Most things that smell are very very small particles not captured by even HEPA filters and require a different kind of filtration. Most commonly activated carbon is used, either as granule or deposited on fibers.

rckoepke 6y ago
HEPA filters are actually more efficient at capturing very very small particles (<0.1 micron) than they are at capturing simply small particles (≈0.3 micron). The tiniest particles are light enough to be captured using electrostatic forces rather than the more typical mechanical filtration that is effective at capturing large particles. More precisely, many odors are not particles at all but rather gases/vapors. Activated charcoal can capture larger organic molecules because it has an incredibly jagged/porous surface - just 100 grams of activated charcoal provides over 1,000,000 square feet of "effective" filtration surface area.
- cyounkins 6y ago
  Yes, that's true that HEPA is very efficient at particles in the 0.01 to 0.1 micron range. It may also be below that, but I personally haven't seen that data. But because HEPA fails to filter gases/vapors, its performance must fall off before 1 angstrom = 0.0001 micron. > odors are not particles at all but rather gases/vapors I think the confusion comes from people referring to "particulate" as particles of >= 0.01 micron, whereas in physics we say that gases/vapors are also composed of particles. They may be single atoms floating (can't actually come up with an example though) or small molecules like O^2, CO, etc, but I'd still call those particles.
  - ClumsyPilot 6y ago
    > 'but I'd still call those particles' But then in your world there are no such things as gasses? If so, the world uses all usefullness
xiphias2 6y ago
I don't know any way to filter NO2 effectively from air, and I have tried practically all commercial air filters with the largest carbon filters on the market. The worst parts of air pollution cannot be filtered out without industrial devices (that are part of the air filteration system) as far as I know.
- ddeck 6y ago
  NO2 and other acidic gases are typically filtered using activated alumina balls impregnated with an oxidizing agent such as potassium permanganate or sodium permanganate. There are residential air purifiers available that use this in combination with activated carbon for their gas stage.
  - xiphias2 6y ago
    I bought IQAir and tried multiple filters (I think they use potassium permanganate), and I wasn't able to significantly reduce NO2 in my room. 3M masks similarly may work if the toxic gas concentration is far above the high levels, but I couldn't get it from normal/high to low levels. Maybe you are talking about an integrated air filtration system, as I haven't tried that yet (though I'm planning to try it).

Havoc 6y ago

Not really. To remove smells ozone generators are used. That stuff is really dangerous though

xnyan 6y ago
This is not correct. Activated carbon is very effective and in wide use for odor removal.
- hajimemash 6y ago
  This is correct, but this is incorrect.
- Havoc 6y ago
  >This is not correct. No it's not. That 200 USD fine for smoking in hotel rooms? What do you think happens afterwards? Buy a bunch of activated carbon filters? Or get a professional ozone odor removal provider to roll in their with their gear?

xnyan 6y ago

To echo everyone else, you want activated carbon. Put it in your filter stack behind the other filter and you’re golden.

heavyset_go 6y ago

I lit a candle in a room where I had one running, and the filter darkened pretty quickly. It seemed to have caught some of the smoke particles, which can be pretty small at under a micron.

Traubenfuchs 6y ago

Smells are usually VOCs (volatile organic compound). Those need to be trapped in an active carbon filter. An alternative is to destroy them with ozone (also called "activated air", "ionized air"), but to do so one needs ozone concentrations that are unhealthy for living beings. Ozone is very unhealthy! Ozone is generated electrically or via UVC lamps. An especially common and harmful VOC, formaldehyde, can be destroyed by the extremely overpriced dyson air filters via their cryptomic technology.