40 ms·

Interesting, it seems that the actual surface material of walls and/or furniture makes a large difference in how long VOCs stick around, due to differences in s

• lm28469 11mo ago
  > HEPA filters They won't do anything against VOCs, you need activated charcoal filters
• throwway120385 11mo ago
  This kinda makes sense. Water vapor diffuses out through the building materials so why wouldn't VOCs diffuse into those materials? What you're looking for are not HEPA filters but organic vapor filtering. If you were shopping for a respirator it would be easy but organic vapor extractors I think are a lot more expensive than HEPA filters. I looked in to it when I was doing a couple of oil based coatings for a home renovation project.
  • wongarsu 11mo ago
    A lot of air purifiers are advertised as HEPA but really contain a filter stack consisting of a pre-filter, a HEPA filter and an activated carbon filter. Those would presumably help against VOCs, assuming you change the filter frequently enough
    • s0rce 11mo ago
      Frequent replacement is critical, my understanding is the activated carbon filters typically provided have very limited capacity. More so when compared to the lifetime of the hepa.
    • bonesss 11mo ago
      Compare those air ‘purifiers’ with the activated charcoal setups they use on cannabis grow operations, and you’ll get a sense of what volume of charcoal and air circulation is necessary to combat those small particulates. Purifiers help in theory but are nowhere near effective or active enough to combat off gassing or VOC dispersals in practice.
    • plorkyeran 11mo ago
      "Frequently enough" with the size of the carbon filter a typical air purifier has would be close to daily.
    • deleted 11mo ago
      [deleted]
• bflesch 11mo ago
  Thats why ecological buildings use lime and clay for plastering indoor walls. They can absorb a lot of things (water, fumes) and thereby regulate air quality and humidity.
  • lxgr 11mo ago
    Do they absorb VOCs forever, though, or do they actually make it harder to vent them out once absorbed by a surface with a large capacity?
    • backprop1989 11mo ago
      I’d think you’d want the VOCs to be captured by something, rather than floating around in the air where you could breathe them in. Combined with a HEPA filter in the air circulation system, this should be a good solution.
      • lxgr 11mo ago
        Absorption is usually not a one-way street, though: Surfaces absorb gasses when the concentration in the air is higher than that on the surface boundary, but often also release them back into the air otherwise (which is why you can e.g. smell cigarette smoke in clothes – if they only captured it, there would be nothing for you to smell). The only difference are some materials like charcoal, which does permanently bind many substances (but as a result can also saturate). No idea which kind lime and clay are (i.e. "absorb and permanently bind with limited capacity" or "act as a buffer both ways"). > Combined with a HEPA filter in the air circulation system HEPA filters are not effective against VOCs.
        • fuzzfactor 11mo ago
          Actually not that many types of things will bind to the carbon permanently, mostly it's the affinity for such a wide variety of contaminants to the carbon, combined with the porosity of the carbon structure which can have a very impressive amount of surface area to come in contact with the fluid being filtered. Whether filtering air or water. It hangs onto contaminants tightly. Because carbon is such an effective adsorbent for contaminants, the partitioning coefficient for contaminants to remain in the solvent being filtered is lowered quite dramatically compared to so many other kinds of affordable alternative filtration media. Most times people do need to afford to discard the carbon eventually, but it doesn't even really absorb contaminants like it's supposed to unless it is activated carbon to a good degree. Activation only means that is it porous enough to begin with so it has enough surface area to be effective, then it is heated with adequate air exchange to about 250 Celsius for as many hours as it takes for virtually all of the VOC's or moisture it may have accumulated to be baked out. Then sealed up tightly, otherwise it can sit around for ages and gradually become saturated passively with any contaminants or humidity admitted through leaks to the ambient environment. Sometimes, you can reactivate almost indefinitely to keep reusing the same carbon, and it works with VOCs because by their volatile nature they are basically baked back out easily and virtually completely each time. Different amounts of time if using different temperatures though, if equipped. The stronger the activation, the more tightly with higher capacity the carbon wants to absorb things it encounters that are dissimilar to the fluid being filtered.
• whatevertrevor 11mo ago
  As pointed out in another comment HEPA filters don't work well for VOCs (Volatile Organic Compounds), which are gaseous in nature. They're intended to filter particulate matter. For VOCs you need activated charcoal/carbon filters usually and replace them from time to time.
  • Gigachad 11mo ago
    Every air purifier I’ve seen has both a hepa filter and carbon filter.
  • jopsen 11mo ago
    Or a ventilation system I'm guess? Where I live all new houses are pressure tested and have a ventilation system, replacing all air once every 1-2 hours or something (I think).
    • sneak 11mo ago
      TFA is specifically about how they attach to porous surfaces and how simple ventilation is way less useful than originally assumed.
      • jopsen 11mo ago
        But when stuck inside the porous surfaces isn't the problem mostly when they become airborne again? Most of us don't eat wooden furniture -- granted my toddler didn't get the memo :) Thus, continuous ventilation (while not perfect) is hopefully still a decent alternative. Probably better than active charcoal filter. Granted I should probably out a charcoal filter on the ventilation intake to reduce pollutants coming in from nearby traffic. (All depending on your level of paranoia)
        • whatevertrevor 11mo ago
          If the porous surfaces are saturated then you'll basically be maximizing the vapor pressure of these gases in the air you breathe. Check out my sibling comment, extrapolating just from the data in the article an active ventilation system should help. EDIT: And yes, charcoal filters aren't as effective if they're not part of your critical airflow/ventilation path. :D
• hxorr 11mo ago
  If you are in a temperate climate, just make a habit of keeping a couple if windows open through the day