[HN Gopher] VOC injection into a house reveals large surface res...
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VOC injection into a house reveals large surface reservoir sizes
Author : PaulHoule
Score : 79 points
Date : 2025-10-12 00:23 UTC (4 days ago)
(HTM) web link (www.pnas.org)
(TXT) w3m dump (www.pnas.org)
| gwking wrote:
| I have never seen the word "partition" used in this way before.
| Hard to search for examples because unrelated computer graphics
| articles about surface partitioning dominate. I did find this:
|
| Partitioning is the distribution of a solute, S, between two
| immiscible solvents (such as aqueous and organic phases). It is
| an equilibrium condition that is described by the following
| equation:
|
| S(aq) = S(org)
|
| Interesting to think that a surface can play a role comparable to
| a solvent. I wonder what a chemist would have to say about it.
|
| https://www.chemicool.com/definition/partitioning.html
| PaulHoule wrote:
| See https://en.wikipedia.org/wiki/Octanol-
| water_partition_coeffi... and
| https://en.wikipedia.org/wiki/Adsorption
| pbhjpbhj wrote:
| In the UK a non-structural wall is called a partition wall --
| they're usually plasterboard (I think that is called sheetrock
| in USA) over wooden studs whilst ordinarily walls are plaster
| on brick/stone.
|
| I wonder which partitions more VOCs/SOCs, partition or
| structural walls.
| PaulHoule wrote:
| More generally partition (as a verb) means "to divide into
| parts" which is used for numerous purposes such as
|
| -- to divide a country into parts (e.g. separate Pakistan and
| Bangladesh from India)
|
| -- to divide a physical space with walls
|
| -- to divide a population of molecules between molecules
| floating in the air and molecules stuck on walls
| lazide wrote:
| Also to divide digital storage into individually
| addressable segments (disk partitions).
| whatevertrevor wrote:
| -- "Divide" an integer into two or more integers that sum
| to it too. :D
| tsimionescu wrote:
| Also to separate a computer network into two or more
| disconnected networks, the P in the CAP theorem stands for
| "partition tolerance" (i.e. that a system can keep working
| in case its components end up in a partitioned network).
| Polizeiposaune wrote:
| A more generic term is drywall or gypsum board. It generally
| is covered by a skim coat of plaster and is then painted.
|
| "Sheetrock" is a particular brand of drywall. For instance,
| see https://www.lowes.com/pl/drywall/sheetrock-
| brand/4294864808-...
| ninalanyon wrote:
| Gypsum board is a considerably more specific, less generic,
| term than partition. My wooden house has some internal non-
| structural walls but none of them use gypsum boards (called
| plasterboard in British English).
|
| Neither are they skimmed with plaster. They are instead
| faced with a very dense and flat hardboard.
| hxorr wrote:
| I think it would depend on what paint is used. Although I
| would strongly suspect exposed porous surfaces like plaster,
| masonry, drywall to have a large reservoir capacity due to
| their surface area at the microscopic level
| s0rce wrote:
| I'm a materials scientist/chemist and the word partition made
| sense in this context. The VOC/solute is preferentially on
| surfaces vs floating in the air. This finding doesn't seem
| super surprising to me given the large surface area of all the
| stuff in a home.
| jagraff wrote:
| 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 surface area at the microscopic
| scale.
|
| I have a couple HEPA filters in my house that hopefully keep
| particulate exposure down. Does this mean that I have to run them
| longer? That I need more of them continuously running to keep
| exposure to VOCs low?
| lm28469 wrote:
| > HEPA filters
|
| They won't do anything against VOCs, you need activated
| charcoal filters
| throwway120385 wrote:
| 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 wrote:
| 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 wrote:
| 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 wrote:
| 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 wrote:
| "Frequently enough" with the size of the carbon filter a
| typical air purifier has would be close to daily.
| bflesch wrote:
| 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 wrote:
| 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 wrote:
| 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 wrote:
| 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.
| bflesch wrote:
| I assume they absorb VOC until you tear down the chalk or
| clay plaster.
|
| With clay the indoor problem is more about radioactivity,
| but it's best in terms of humidity control. Chalk creates
| an alkaline environment on the surface which makes it
| inhabitable for mold (however the wooden furniture you put
| in front of it can still get mold if the indoor air
| humidity is too high).
| scottlamb wrote:
| Does that work if it's painted over? Or can you mix colorants
| in as with (exterior) stucco? (Maybe this _is_ considered a
| kind of stucco? I just had to look it up: wikipedia says
| "The basic composition of stucco is lime, water, and sand".)
| ender341341 wrote:
| I would assume if you paint it over with a latex based
| paint at least it would massively affect absorption. For
| oil based paints I have no idea though.
| bflesch wrote:
| Nope, I dont think it works when painted over. Some vendors
| recommend colors which are very open for diffusion such as
| chalk colors, but every other "common" color based on
| acryl/latex/etc basically seals it from the air and
| destroys it over long term.
|
| For clay I know you can add color pigments to the clay
| itself, most likely you can do the same with stucco for
| some limited amount of colors. But painting over it with
| modern products mostly destroys the diffusion properties.
|
| Many people put plastics or other sealing products on top
| of a clay or lime-based wall and it's a shame.
| bahmboo wrote:
| The paper posits this is a problem. Large amounts of VOCs are
| absorbed by these complex structures. Then the structures
| with the embedded VOCs flake off and are absorbed by
| breathing, dermal contact and ingestion. Particularly by
| small children. This is literally their point.
| whatevertrevor wrote:
| 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.
| jopsen wrote:
| 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 wrote:
| TFA is specifically about how they attach to porous
| surfaces and how simple ventilation is way less useful than
| originally assumed.
| jopsen wrote:
| 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 wrote:
| 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
| whatevertrevor wrote:
| The GP comment is talking about active ventilation
| though, through an ERV/HRV system. Also the article
| states this:
|
| > The lifetime of these compounds indoors can be extended
| via partitioning to the surface reservoir as modulated by
| ACR. Higher ACR, which may be achieved by opening windows
| or through mechanical ventilation, leads to shorter
| t_half_surf because once indoor compounds partition from
| the surface reservoir to the gas phase as controlled by
| gas diffusion across the boundary layer, they would be
| removed from indoor air more quickly before
| repartitioning to the surface reservoir.
|
| So they do state active ventilation can help, as you
| reduce the vapor pressure of VOCs allowing them to
| partition back into the gaseous env, where they can be
| promptly ejected. How much exactly is hard to ascertain
| from their graph since I don't have the exact data they
| used in the plots. But from squinting at it, it seems 1
| OOM change in ACR gives you close to 1 OOM change in the
| VOC half life, which seems substantial to me.
|
| So adding an active ventilation system might be a good
| idea for this particular concern. Of course it will add
| to your energy bill.
| hxorr wrote:
| If you are in a temperate climate, just make a habit of keeping
| a couple if windows open through the day
| lxgr wrote:
| Reminds me about this recent Reddit thread where somebody ran an
| Ozone generator in a house for hours to get rid of smells, and in
| exchange ended up with a much worse situation:
| https://www.reddit.com/r/chemistry/comments/q949go/holy_shit...
|
| VOCs getting absorbed by surfaces was the most plausible theory
| in the comments there as well. Interesting to see more evidence
| for it.
| bob1029 wrote:
| I've ran an ozone generator in a house for multiple days, but I
| went into it with the expectation that it would be
| uninhabitable for a period of time afterward.
|
| Ozone won't stick around for very long. It is extremely
| reactive. With windows / doors open and vent fans running it
| will be cleared out in maybe a few hours max. The first few
| minutes is definitely overpowering though. You need to have a
| plan to turn the machine off and ventilate the building that
| doesn't involve walking through it for longer than you can hold
| your breath.
| mindslight wrote:
| I just wore a half face respirator with an activated carbon
| filter (3M 7503 + 6001 + something over that for
| particulates, probably 2297). Quality respirators seem like
| simple table stakes for doing a lot of things these days. It
| was an off label use of the organic vapor cartridge but it
| worked fine (it also worked fine for cleaning with ammonia in
| deep cabinets). I also probably plugged the O3 generator into
| an extension cord which I could unplug without going in the
| room, the mask was just to go in and open the windows some
| time afterwards. It seems like, as with anything, the
| important part is to know the technicals of what something
| does and create an overall plan.
| ok_computer wrote:
| I've used respirators through prior lab work and be warned
| the ammonia grade and organic solvent grades are distinct
| filter packing.
| mindslight wrote:
| Sorry, that's what I meant to imply about off label use.
| I should have stated it explicitly.
|
| Household cleaning one would otherwise moderate their
| exposure "by smell", so I'm comfortable trusting my sense
| of smell through an activated charcoal filter even though
| it's not a listed use, is past expiration, etc.
|
| For things (eg painting with isocyanates), I follow the
| directions religiously.
| fhdkweig wrote:
| Coincidentally, Technology Connextras (the low-effort side
| channel for Technology Connections) posted a video this week on
| ozone generators. He swears by them.
|
| https://www.youtube.com/watch?v=RYKpKMFIdGQ
| mikkupikku wrote:
| I had the idea to use an ozone generator in my car once but
| backed off due to a concern about it degrading interior
| rubbers and plastics. I guess that's not much of a real
| concern in practice though.
| arcanemachiner wrote:
| If you don't overdo it (like the guy in the reddit post
| did), it works great. 5 to 10 minutes with the car fan
| recirculating the air, repeat once or twice if needed. Just
| make sure you don't breathe the ozone.
| mmmlinux wrote:
| 5-10 minutes might get a bad fart out, but any real
| amount of cigarette smoking is going to take a few hours
| of cooking.
| plorkyeran wrote:
| It's a mild concern, but if you need enough ozone to cause
| meaningful damage then the smoke has probably ruined the
| car anyway. The key is to run it just barely long enough.
| mikkupikku wrote:
| In my case the smell came from running over a rotten deer
| carcass. I settled on about a dozen trips through an
| undercarriage carwash them leaving the windows all open
| for a month. I figured the smell would go away eventually
| so I wasn't eager to risk long term damage from ozone,
| but my god was the smell awful for the first week.
| throwaway173738 wrote:
| I've used Simple Green to remove nicotine before. In a
| house you can also paint over it with shellac primer.
| LeifCarrotson wrote:
| Sorry to break it to you, but your "recent" thread is 4 years
| old.
|
| I have a cheap ozone generator I've used for cleaning cars and
| boxes of used books. Used at the right concentrations and
| durations, it's magical! Run it outside or in a sealed tote.
|
| But yeah, they'll sell them to just anyone. Electricity and air
| go in, and ozone (a reactive, toxic chemical) comes out for as
| long as you leave it plugged in.
| boringg wrote:
| Books?
| fhdkweig wrote:
| In a smoker's household, everything reeks of the smell for
| years. And the porous nature of paper causes it to retain
| the smell too.
| LeifCarrotson wrote:
| Yeah, they're like a Kindle, but instead of one screen that
| changes they have hundreds that remain static.
|
| DRM-free, too, and made from an eco-friendly carbohydrate
| foam!
| DougN7 wrote:
| Lol - excellent!
| lxgr wrote:
| Storage capacity remains an issue, though.
| Ekaros wrote:
| Is it really DRM-free if making copies is really hard
| process and you even need to crack part of it(spine). Or
| even worse remove part(the binding)...
| fujigawa wrote:
| I chuckled at his indignance over how these things are legal
| and how easily you can buy them. Chinese will sell you anything
| to make a buck. It's just business. You can go on Amazon right
| now and buy a high power 1kW FM transmitter, drop shipped, and
| set up a flamethrower pirate radio station on a rooftop of your
| choosing. The cherry on top is they are likely super low
| quality with crazy spurious emissions.
|
| Of course the FCC will probably be up your ass in half an hour
| if you tried it; the point is the equipment is readily
| available in a few clicks, no questions asked.
|
| Don't get me started on the instantly-blind-yourself-and-
| everyone-else lasers you can buy on eBay (they'll sell you
| matching counterfeit laser goggles too).
| crote wrote:
| It would be "the Chinese will sell you anything" if they
| bought it on Alibaba and imported it on their own.
|
| If you buy it on Amazon, it's "the Americans will sell you
| anything". If Amazon is too lazy to do due diligence on their
| third-party sellers, the blame should fall on Amazon if the
| item turns out to be illegal or dangerous.
|
| Amazon _chose_ to make direct fulfilment almost
| indistinguishable from third-party fulfilment. Don 't want to
| be treated like a regular store? Then don't make your
| marketplace behave exactly like a regular store for the
| buyer!
| cyanydeez wrote:
| Nothing to do with china. Americans will sell these things
| markdown wrote:
| I mean numerous US companies sell caffeine powder on Amazon
| as a supplement for gym and tech bros. A teaspoon of it will
| kill a grown man.
| XorNot wrote:
| "I can't find any information on how to get rid of lingering
| ozone"
|
| I'd feel embarrassed if I was their alma mater reading that.
| quickthrowman wrote:
| The proper way to get rid of smells from a smoker is to wash
| all of the paintable surfaces with trisodium phosphate, paint
| all of the walls and ceilings with Kilz primer, and then clean
| the floors, doors, and woodwork (and everything, windows, etc)
| with a solvent that removes the tar and resin (or paint them
| with Kilz too). If there is carpet, remove the carpet and pad
| and install new carpet. Might need to replace fixtures and
| furnishings depending on how bad it is.
|
| So yeah, smoking in a house is insanely destructive and takes a
| long time to actually remove the odor forever.
|
| Also, check all of the drains (including floor drains) to
| ensure there is water in the trap.
| DoneWithAllThat wrote:
| As with so many headlines like this, it should read (title),
| claims a single unreplicated study.
| colechristensen wrote:
| No it does not need that.
|
| Replication and peer review are required to be very careful
| about believing small effect sizes that are inconsistent across
| populations which are so common with papers in biology and
| medicine measuring the effect of _X_ on _Y_ when it 's entirely
| believable that the study might just be statistical error or
| cherry picking.
|
| This study is measuring something pretty obvious and it's more
| akin to you demanding replication and peer review to your
| bathroom scale. There might be room for some additional studies
| but the conclusions here "surface areas for VOCs to stick to
| are much bigger than this simplified model" don't really need
| to be doubted all that much.
| anarticle wrote:
| Does this mean the Germans are right with Luften!? I habitually
| have done this as an American in the morning for my office,
| something about morning fresh air after the night seems right?
| tecleandor wrote:
| They usually do it for avoiding condensation, hence mold. New
| german buildings are very well insulated (sometimes too much)
| so you gotta move that condensation humidity.
| Groxx wrote:
| > _Our estimates of the total surface partitioning capacity are
| much larger than if the reservoirs are taken to be thin organic
| films on smooth, impermeable surfaces._
|
| ... so is "smooth, impermeable surfaces" the current
| begrudgingly-accepted model or something? because there's no way
| any person who has ever been in a house would think that's a
| reasonable model. permeable surfaces are _all over the place_ ,
| literally _most of the place_ because it includes essentially all
| walls and therefore wall interiors. managing that for e.g.
| humidity is a significant part of building design because it 's
| completely inescapable... and that's before even touching stuff
| like fabric where your average couch probably has more surface
| area than all structural surfaces combined.
| frickinLasers wrote:
| Yes, it probably is. Have you ever heard of the spherical cow?*
|
| Simplifying the surface makes it possible to model the system
| with equations that can be solved analytically--which gives
| theorists something to work on. Modeling more complex systems
| (which often happens, eventually) typically requires lots of
| computing power and results in a model that doesn't generalize
| well.
|
| * https://www.sphericalcowblog.com/spherical-cows
| strongpigeon wrote:
| That reminds me of when I was living right by the BLM
| protests/CHOP [0] in Seattle and got tear gas in my condo. I had
| just bought some new coffee beans to try out and when I did the
| next morning, thought they tasted super "chemical-y" and
| immediately threw them aways.
|
| Turns out tear gas is known to seep into food items, especially
| porous food like coffee and bread [1]. Not surprised at all that
| VOCs linger in reservoirs as mentioned in the article.
|
| [0]: https://en.wikipedia.org/wiki/Capitol_Hill_Occupied_Protest
|
| [1]: https://www.propublica.org/article/tear-gas-is-way-more-
| dang...
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