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Author Topic: Replacing the Oxygen In Your Home - even with withe windows shut !  (Read 6712 times)

Offline neilep

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Dear All,

We all know fresh air is good for you !..though...I've worked in central London and sometimes the freshest air is inside !

I am curious............. that besides the occasional opening and closing for entrance and exit from your home..how quickly is the air replenished in lets say a standard three/four bedroomed home ? assuming all the windows are closed and that there are no vents and the chimneys are blocked ?

Is todays air in my home the same as yesterdays ?......if it is.......how long before I am breathing new air !! ?



 

another_someone

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No domestic dwelling is totally draught proof (i.e. hermetically seeled), and would be dangerous if it were.
 

Offline Seany

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Yes.. Everywhere is not completely seeled. Even your doors, there is like a 2-3mm gap on the bottom etc. Even our cars, as seeled as it looks, air can still pass through some gaps there. ;)
 

Offline neilep

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Thanks guys,

So, how long before I can safely say that the air in my house is replaced ?
 

Offline Seany

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I don't understand you question.

Air is always replaced..?
 

Offline neilep

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I want to know when I can be sure that every air molecule that is in my house right NOW,,this INSTANT is evacuated from my house and replaced by a whole new bunch of air !!

 

Offline Seany

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Neil ya dummy.

We breathe out right? We RESPIRE

What's the formula matey?

Oxygen + Glucose --> Carbon Dioxide + Water + (Energy)

We will always give off Carbon Dioxide in the respiration process. So we cannot clearly say, when all the gases in our house are completely replaced by oxygen, because unless you make a vacuum within the house, it would probably still be impossible, as Nitrogen and Carbon Dioxide from outside will come into our houses aswell as the Oxygen. There is about 70% of Nitrogen in the air!
 

Offline neilep

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Neil ya dummy.

We breathe out right? We RESPIRE

What's the formula matey?

Oxygen + Glucose --> Carbon Dioxide + Water + (Energy)

We will always give off Carbon Dioxide in the respiration process. So we cannot clearly say, when all the gases in our house are completely replaced by oxygen, because unless you make a vacuum within the house, it would probably still be impossible, as Nitrogen and Carbon Dioxide from outside will come into our houses aswell as the Oxygen. There is about 70% of Nitrogen in the air!

*le sigh*...okay....thanks Seany !.................say the house is empty and void of plants !!
 

Offline Seany

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Yes.. But through the little holes and cracks and everything. Nitrogen and Carbon Dioxide will seep through?
 

Offline neilep

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Yes.. But through the little holes and cracks and everything. Nitrogen and Carbon Dioxide will seep through?

Yes, I am well aware of that..in fact THAT is the whole pont of my post !!...... Seany me old mucker !!!!..that is why I am asking how long before the air that is inside the house becomes replaced with air form outside the house which will then become inside the house as the inside air seeps through to the outside via gaps and leaks and stuff !!...I never said anything ever about the house being hermetically sealed ... ;D ;D
 

Offline Seany

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Yes.. But aren't there thousands of factors for that, so we cannot actually measure it?

1. All houses are different sized
2. Some are more or less seeled than others
3. Wind helps with air seeping through. Depends where you live.


Right?
 

Offline neilep

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Yes.. But aren't there thousands of factors for that, so we cannot actually measure it?

1. All houses are different sized
2. Some are more or less seeled than others
3. Wind helps with air seeping through. Depends where you live.


Right?
*le sigh* Do you know how to formulate a premise ?

read my initial post...I am talking ' generalizations' here !!...I am not providing you with a schematic of a building with the internal cubic capacity..I am asking about a bog standard 3/4 bedroomed house !!


If we had to be so pedantic we'd spend hours just agreeing on the question !!!.....you're supposed to humour me !!..LOL
 

Offline Seany

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Heehee. I am sorry. I still do not understand!



Pssssssst. Someone come along and help me!!!!
 

Offline neilep

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No worries...I've obviously gone and buggered up with the way I word things !!

One symptom of Insomnia !!.....Bear in mind I've been awake since Sunday morning !

I know what I mean...LOL

 

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I doubt you can talk about the air being totally replaced, but rather, a certain percentage of the air being replaced.

At least one molecule of air will be replaced within milliseconds, but some molecules of air might remain trapped within some crevice for decades.

http://www.afhh.org/aa/aa_housing_codes_ventilation.htm
Quote
IRC § 303.1: Light, Ventilation, and Heating/Habitable Rooms. Habitable rooms must be provided with total glazing (window) area of at least eight percent of the room’s floor area. Natural ventilation must be provided through readily controllable windows, doors, etc. Minimum openable area to the outdoors must be four percent of the room’s floor area. Windows need not be openable if they are not needed for emergency exit and a mechanical ventilation system is capable of producing 0.35 air change per hour in the room, or a whole-house ventilation system is installed capable of supplying outdoor air at 15 ft³ per minute per occupant, with occupants computed based on the number of bedrooms.

The above does not I think directly answer your requirement exactly, since it merely states that ventilation should be sufficient to replace 0.35 of the air each hour, but it does not, at least to my reading, suggest that this remains true even if the windows are closed (it just suggests that if the windows cannot be opened, then this rate of exchange should still be possible).
« Last Edit: 17/04/2007 17:49:24 by another_someone »
 

Offline neilep

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Thank you George,

Every bit of info is useful and that quote is quite appropriate !

Do you think that a very rough general way of finding out would be to fill the house with smoke and measure how long it took before the house is smoke free !!..of course one have to use precise smoke detectors..

I realise then that the smoke in itself is  inherent due to the nature of what kind of smoke it is....' air weight' smoke would be good !!..

LOL...I think this thread has died a death !!.....just like my cognitive abilty !!
 

Offline Seany

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Hmm.. Neil. But does smoke diffuse at the same time as Carbon Dioxide or Oxygen?
 

Offline neilep

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Hmm.. Neil. But does smoke diffuse at the same time as Carbon Dioxide or Oxygen?




grrrrrrrrrrrrr !!!...LOL !!!
 

Offline Bored chemist

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Hi Neil,
Do you mean that, if you could label all the molecules of the air in your house (I think painting them purple would be a good way to do it) and then you left the house, how long would it be before there were no purple molecules left?
If so I think the answer is never. If you emptied out the air- say you opened the windows on a windy day- and then mixed all the purple air with the rest of the atmosphere and refilled your house there would always be some of the purple molecules in your house.
The atmosphere weighs something like 14.7 pounds per square inch. That's about 50 tons to the square metre. It covers something like 150,000,000 square km so, in total it weighs about 7.5x10^18 Kg (Google seems to give an answer rather less than that, but it hardly matters).
A cubic metre of air weighs about 1.2Kg so my house (I don't know how big your house is) holds about 300Kg of air. So the atmosphere is about 2x10^16 houses full. If you painted a houefull of air purple and mixed it up with the rest of the air about in molecule in 2X10^16 would be purple
However a house contains something like 6x10^27 molecules,  so if one in 2x10^16 is purple, then a housefull would contain something like 3x10^11 purple molecules.
Of course, you can't really label the molecules, but the maths is the same anyway.

By the way the diffusion rates for gases (all other things being equal) vary as the reciprocal of the square root of the molecular weight; it's called Graham's law.
 

Offline neilep

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Hi Neil, HI BC,
Do you mean that, if you could label all the molecules of the air in your house (I think painting them purple would be a good way to do it) and then you left the house, how long would it be before there were no purple molecules left? YES !!
If so I think the answer is never. Oh really, how come ?..If you emptied out the air- say you opened the windows on a windy day- and then mixed all the purple air with the rest of the atmosphere and refilled your house there would always be some of the purple molecules in your house. Aha..I see !!
The atmosphere weighs something like 14.7 pounds per square inch. Cripes..that's a lot !! That's about 50 tons to the square metre. That sounds even more !! It covers something like 150,000,000 square km so, in total it weighs about 7.5x10^18 Kg (Google seems to give an answer rather less than that, but it hardly matters).
A cubic metre of air weighs about 1.2Kg so my house (I don't know how big your house is) holds about 300Kg of air. So the atmosphere is about 2x10^16 houses full. If you painted a houefull of air purple and mixed it up with the rest of the air about in molecule in 2X10^16 would be purple
However a house contains something like 6x10^27 molecules,  so if one in 2x10^16 is purple, then a housefull would contain something like 3x10^11 purple molecules.
Of course, you can't really label the molecules, but the maths is the same anyway. Wow !!..nice calculations !!

By the way the diffusion rates for gases (all other things being equal) vary as the reciprocal of the square root of the molecular weight; it's called Graham's law. Good old Graham !

THANK YOU BC....thank you very much !
 

Offline Batroost

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Nice elegant post BC.  [8D]
 

Offline Bored chemist

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You can't beat a post full of purple air molecules.
 

Offline neilep

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You can't beat a post full of purple air molecules.

I am just sorry I tainted it with pukey orange font yukkiness !!
 

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