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.
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.
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.
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).
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!
Coincidentally, Technology Connextras (the low-effort side channel for Technology Connections) posted a video this week on ozone generators. He swears by them.
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.
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.
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.
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.
For inhabited spaces there are ionizers available optimized to produce negligible amounts of ozone. They produce O2- and N2- ions instead, which are much safer, even beneficial. They help not only with VOCs but dust too unlike ozone which is a neutral molecule.
The confusion with ozone generators is understandable but very unfortunate here.
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.
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.
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.
> 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.
This is by far the most Seattle thing I have ever read.
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.
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.
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.
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).
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.
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
In separation science a partitioning coefficient can be described for an undesirable contaminant, inbetween a solid adsorbent having a certain degree of retention, versus a solvent where it is soluble to its own certain degree, under static equilibrium conditions.
IOW the smoke will have different affinity for different types of furniture, carpets, and window coverings, and when it comes in contact with these they soak it up like a sponge. Because the adsorbent materials are physically like a sponge more often than not, whether on a macro, micro, or molecular level.
The solvent is plain air, but the "solubility" of the raw smoke in air is not a factor because the smoke is not actually dissolved in the solvent (air) at this point, or ever really. The smoke consists of a lot of solid particles that have been forcefully dispersed into the air at uneven concentrations. The smoke itself is not a chemical contaminant that dissolves in the air, it's just dispersed in the air not much differently than an unwanted chemical, for a least a good period of time.
But the solids will eventually settle if they are not purged beforehand. What you're left with after that is then chemical equilibrium.
In a confined enclosure, static equilibrium will eventually be reached between the amount of chemical contaminants dissolved in the air at that temperature, versus the amount adsorbed onto available surfaces. After which no more odor can be released from the furniture once the air is saturated. To really get rid of the smell you're going to have to replace the saturated air with fresh air and one compete air exchange is not usually enough. Also the more efficient air exchange the better, and the fresher the better. If one person smoked one time, or you burned some popcorn and did not let out the smoke right away, that's not much contamination and it's not constant, but it's also not unusual to still smell it a week later when you first walk in from a fresh outdoor air environment. But just don't open the windows when something like a diesel truck is idling outside, new odor could then be coming in in greater quantities than the old odor can escape, one roomful at a time.
You may have grams of "odor" soaked into the carpet along with 100 grams of dirt & dust. But what if the chemical causing the odor only "evaporates" into the air a few milligrams at a time? Because the heavier the liquid, the slower the evaporation and the resulting partitioning coefficient using air as a solvent is such a low number. And it's not too unintuitive to figure that things which are semi-solid like tars or true solids like some pesticides hardly evaporate at all, but can really stink when there's only a few milligrams in the air.
Stuff like that is not going away without a solvent much stronger than air, and also a more concentrated solvent than a gaseous fluid can make contact by the gram much faster than a gram of fresh air can eventually flow by the unwanted material to be removed.
Plain water may not be any better as a solvent at dissolving cooking oils and tars than air is a solvent, but you sure can get a lot more grams into contact with a surface or macro adsorbent quicker compared to air as a gas.
Plain steam dissolves things so much better just from the added heat of the liquid turning it into a stronger solvent, plus so much of the water evaporates so fast at that temperature there is also a purging effect.
Then there's the carpet-cleaning liquids that can improve the partitioning coefficient of water so it will dissolve otherwise insoluble materials without nearly as much heat as steam. Like grams of detergent added to volumes of water to clean a certain area of carpet, or hundreds of grams of water-soluble organic solvent over the same area instead. Or both, simultaneously, or sequentially. Then when you do the math you see how much more effective sequentially is.
Now without doing any carpet cleaning, when you enhance the air exchange rate to do as good a job removing odors as that can accomplish, you are then trying to establish a dynamic equilibrium so odors are being purged outward at an enhanced rate due to increased fresh solvent (air) flow. Kind of like sequential carpet cleaning. One window fan blowing in and one blowing out at opposite ends of the structure can sometimes be more effective than all windows open whether or not using the same fans.
>I wonder what a chemist would have to say about it.
I wouldn't be surprised if people are still wondering :)
Edit: Hopefully they're wondering even more about a lot of things where they didn't know there were equations, actually ;)
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?
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.
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.
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)
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
True, but simply using a low volume exhaust like a bathroom fan can give you a phenomenally greater effect than zero.
And that's for the entire house, zero is such a small number.
Then when you run it 24/7 it's 24 times as effective compared to a single hour. That's an impressive multiple itself, on top of bumping the baseline above zero to begin with.
This can really add up to a lot more ventilation than commonly assumed from some of the crummiest fans.
If you can't tell the difference when you walk in, between zero and running one of these all day before you get there, you're gonna need a bigger fan.
But you may be surprised and you never know until you try.
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.
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
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.
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.
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.
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.
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.
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
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).
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".)
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.
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.
>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.
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.
Does this mean the Germans are right with Lüften!? I habitually have done this as an American in the morning for my office, something about morning fresh air after the night seems right?
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.
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.
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.
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.
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.
I’ve used respirators through prior lab work and be warned the ammonia grade and organic solvent grades are distinct filter packing.
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.
> It is extremely reactive.
It's two oxygen atoms with 1.5 covalent bonds each and another one in the middle with three!
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).
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!
Nothing to do with china. Americans will sell these things
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.
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
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.
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.
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.
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.
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.
The lesson from the thread is to start small and work your way up, instead of just nuking it.
I’ve used Simple Green to remove nicotine before. In a house you can also paint over it with shellac primer.
For inhabited spaces there are ionizers available optimized to produce negligible amounts of ozone. They produce O2- and N2- ions instead, which are much safer, even beneficial. They help not only with VOCs but dust too unlike ozone which is a neutral molecule.
The confusion with ozone generators is understandable but very unfortunate here.
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.
Books?
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!
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)...
Storage capacity remains an issue, though.
Lol - excellent!
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.
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.
"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.
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...
> 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.
This is by far the most Seattle thing I have ever read.
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
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.
See https://en.wikipedia.org/wiki/Octanol-water_partition_coeffi... and https://en.wikipedia.org/wiki/Adsorption
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.
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
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).
-- "Divide" an integer into two or more integers that sum to it too. :D
Also to divide digital storage into individually addressable segments (disk partitions).
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-...
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.
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
In separation science a partitioning coefficient can be described for an undesirable contaminant, inbetween a solid adsorbent having a certain degree of retention, versus a solvent where it is soluble to its own certain degree, under static equilibrium conditions.
IOW the smoke will have different affinity for different types of furniture, carpets, and window coverings, and when it comes in contact with these they soak it up like a sponge. Because the adsorbent materials are physically like a sponge more often than not, whether on a macro, micro, or molecular level.
The solvent is plain air, but the "solubility" of the raw smoke in air is not a factor because the smoke is not actually dissolved in the solvent (air) at this point, or ever really. The smoke consists of a lot of solid particles that have been forcefully dispersed into the air at uneven concentrations. The smoke itself is not a chemical contaminant that dissolves in the air, it's just dispersed in the air not much differently than an unwanted chemical, for a least a good period of time.
But the solids will eventually settle if they are not purged beforehand. What you're left with after that is then chemical equilibrium.
In a confined enclosure, static equilibrium will eventually be reached between the amount of chemical contaminants dissolved in the air at that temperature, versus the amount adsorbed onto available surfaces. After which no more odor can be released from the furniture once the air is saturated. To really get rid of the smell you're going to have to replace the saturated air with fresh air and one compete air exchange is not usually enough. Also the more efficient air exchange the better, and the fresher the better. If one person smoked one time, or you burned some popcorn and did not let out the smoke right away, that's not much contamination and it's not constant, but it's also not unusual to still smell it a week later when you first walk in from a fresh outdoor air environment. But just don't open the windows when something like a diesel truck is idling outside, new odor could then be coming in in greater quantities than the old odor can escape, one roomful at a time.
You may have grams of "odor" soaked into the carpet along with 100 grams of dirt & dust. But what if the chemical causing the odor only "evaporates" into the air a few milligrams at a time? Because the heavier the liquid, the slower the evaporation and the resulting partitioning coefficient using air as a solvent is such a low number. And it's not too unintuitive to figure that things which are semi-solid like tars or true solids like some pesticides hardly evaporate at all, but can really stink when there's only a few milligrams in the air.
Stuff like that is not going away without a solvent much stronger than air, and also a more concentrated solvent than a gaseous fluid can make contact by the gram much faster than a gram of fresh air can eventually flow by the unwanted material to be removed.
Plain water may not be any better as a solvent at dissolving cooking oils and tars than air is a solvent, but you sure can get a lot more grams into contact with a surface or macro adsorbent quicker compared to air as a gas.
Plain steam dissolves things so much better just from the added heat of the liquid turning it into a stronger solvent, plus so much of the water evaporates so fast at that temperature there is also a purging effect.
Then there's the carpet-cleaning liquids that can improve the partitioning coefficient of water so it will dissolve otherwise insoluble materials without nearly as much heat as steam. Like grams of detergent added to volumes of water to clean a certain area of carpet, or hundreds of grams of water-soluble organic solvent over the same area instead. Or both, simultaneously, or sequentially. Then when you do the math you see how much more effective sequentially is.
Now without doing any carpet cleaning, when you enhance the air exchange rate to do as good a job removing odors as that can accomplish, you are then trying to establish a dynamic equilibrium so odors are being purged outward at an enhanced rate due to increased fresh solvent (air) flow. Kind of like sequential carpet cleaning. One window fan blowing in and one blowing out at opposite ends of the structure can sometimes be more effective than all windows open whether or not using the same fans.
>I wonder what a chemist would have to say about it.
I wouldn't be surprised if people are still wondering :)
Edit: Hopefully they're wondering even more about a lot of things where they didn't know there were equations, actually ;)
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?
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.
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).
TFA is specifically about how they attach to porous surfaces and how simple ventilation is way less useful than originally assumed.
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.
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)
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
True, but simply using a low volume exhaust like a bathroom fan can give you a phenomenally greater effect than zero.
And that's for the entire house, zero is such a small number.
Then when you run it 24/7 it's 24 times as effective compared to a single hour. That's an impressive multiple itself, on top of bumping the baseline above zero to begin with.
This can really add up to a lot more ventilation than commonly assumed from some of the crummiest fans.
If you can't tell the difference when you walk in, between zero and running one of these all day before you get there, you're gonna need a bigger fan.
But you may be surprised and you never know until you try.
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.
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
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.
"Frequently enough" with the size of the carbon filter a typical air purifier has would be close to daily.
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.
> HEPA filters
They won't do anything against VOCs, you need activated charcoal filters
If you are in a temperate climate, just make a habit of keeping a couple if windows open through the day
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.
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.
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?
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.
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.
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).
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".)
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.
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.
>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.
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
Does this mean the Germans are right with Lüften!? I habitually have done this as an American in the morning for my office, something about morning fresh air after the night seems right?
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.
It helps a lot with CO2 accumulation as well which is a problem in a tight house.
As with so many headlines like this, it should read (title), claims a single unreplicated study.
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.