How does sealed aircondition room get oxygen so we not suffocated?

[paulcheung]

Hi all,

I always wonder how the hotel rooms get oxygen in the rooms that people don't suffocated? They sealed te doors and windows, the air condition in there does not have intake pipe from outside like the first time window unit that have options you can turn on fresh air or recycle air like the car aircondition.

Does those aircondition regenerate oxygen? I hope some engineer can coming and provide an answer.
Thank you.

 

[jagec]

Hotel rooms aren't truly sealed, and humans don't use that much oxygen in comparison to the rate at which the air gets exchanged. I wouldn't run a generator in a hotel room, though.

 

[Sub Zero]

I had thought true AC would require some sort of air exhaust, like the portable models you can buy at Costco.

They may have passive vents in the room in order to provide equalized pressure. Some have active and passive in bathrooms.

 

[Murloc]

I guess they have central A/C?

and if the bathroom is sealed (no windows that can be opened), there is always a small duct with a fan to air it.

I don't think there will ever be an A/C that regenerates oxygen in a hotel room on earth.

 

[paulcheung]

I always feel bad when I sleep in a hotel at the night, The strange thing is that I don't feel that way during the day. I always open the window a little crack if is possible. but most of them are seal now.
Thanks

 

[jackofalltrades]

No none of the rooms are sealed. The a/c units have to allow a little fresh air in there just isn't any adjustment for the mixture. The reason you don't feel good is because of the dust and dirt build up in motel rooms. I would venture to say if you checked 90 percent of the motel rooms you would find dust build up on the horizontal planes, most never even wipe behind the TV, because it is bolted down.
If you leave the window cracked open you are adding less dust laden air into the room.
My wife has worked in the past in motels and the time alloted to clean most rooms isn't sufficent to do much cleaning.

 

[Wizlem]

A person expends about 2000 calories in a day so in a night about 667. Now most of that is received from sugar at about 4 calories per gram so about 167 grams. About 40% of that is actually carbon atoms so about 67 grams of carbon is released by a human in 8 hours. This means about 178 grams of oxygen is used up to make CO2. If we assume air is mostly made of similar weight particles, a 27 cubic meter room will have about 6.8kg of oxygen in it. The reduction in oxygen by you being in it is thus less than 3%. I'd imagine that is really insignificant and also a 27 cubic meter room is pretty small so the number would be lower if you are in a decent hotel room.

 

[piasabird]

Eventually some air probably sneakes in when you go in and out. One thing that happens is that air pressure would become less if you used all the oxygen, and then the outside air would have higher pressure and try to force its way in through any crack or crevice inclucing every little pinhole, doors, vents, etc. Most central air systems have a way of adding air from the outside. I know at my house the furnace brings in air from the outside.

 

[NeoPTLD]

Leakage rate exceeds oxygen consumption rate for a person.

 

[pandemonium]

No building is built as air tight as you think; especially hotels that are otherwise built against a general contractor's profit margin.

 

[paulcheung]

Most of the hotel rooms are not central air conditioning, they use the split unit that don't have any air intake, but if the calculation is right by you guys then it is ok because the doors will open and close during the day. and I believe the hall and passages are central air conditioned.
Thanks.

 

[CycloWizard]

No building is built as air tight as you think; especially hotels that are otherwise built against a general contractor's profit margin.

Curse the evil profits that keep you alive!!!

For anyone interested in the reality of the situation, you can easily google building codes and how many "air changes" per hour are required in a given type of building. I believe the relevant codes are published by ASME.

 

[edcarman]

Oxygen is an atom

Water is a molecule consisting of 2 hydrogen and 1 oxygen atoms, so a water molecule is a lot larger than an oxygen atom.

I don't think this is right. Most oxygen in the air is in the form of O2 molecules, which I believe are bigger than water molecules. I think N2 and CO2 molecules may also be bigger.

In most cases, water tight refers to liquid water, not gases or water vapour. I think the actual explanation will have something to do with the properties of a liquid vs. a gas. Maybe surface tension or something like that. Just look at a fabric like Gore-Tex - it repels liquid water, but allows water vapour to pass through.

 

[KIAman]

I don't think this is right. Most oxygen in the air is in the form of O2 molecules, which I believe are bigger than water molecules. I think N2 and CO2 molecules may also be bigger.

In most cases, water tight refers to liquid water, not gases or water vapour. I think the actual explanation will have something to do with the properties of a liquid vs. a gas. Maybe surface tension or something like that. Just look at a fabric like Gore-Tex - it repels liquid water, but allows water vapour to pass through.

Water is significantly heavier than air so something that is rated "waterproof" must withstand a lot more pressure than something that is "airtight."

Thus the reason waterproof rating is based on meter depth, which roughly translates to pressure.

 

[Jeff7]

Bugs and mice can get into buildings and the rooms within. (Though some of them will make their own openings.) Oxygen molecules will have no problem doing the same.
The walls themselves are also permeable to gases, just not like a screen door or a tissue.

 

[Throckmorton]

A sealed room doesn't get enough oxygen. A modern building is so well sealed that CO2 reaches levels over the course of a night that can affect your brain.

For a single person to get enough ventilation, a window has to be cracked about 1". Add an inch for each additional person.

The only reason no one realizes this is because we don't have CO2 detectors in our houses.

 

[Throckmorton]

No building is built as air tight as you think; especially hotels that are otherwise built against a general contractor's profit margin.

Yes they are, compared to how much ventilation you actually need. A space small enough for ants to crawl through isn't enough for CO2 to stay at the atmospheric level of about 380ppm. Over 8 hours it can reach 5000ppm in a normal size bedroom I believe. If I could find the study I'd post it.

 

[Wizlem]

Yes they are, compared to how much ventilation you actually need. A space small enough for ants to crawl through isn't enough for CO2 to stay at the atmospheric level of about 380ppm. Over 8 hours it can reach 5000ppm in a normal size bedroom I believe. If I could find the study I'd post it.

This isn't that hard to calculate if you read my previous post, There is definitely an upper limit on the amount of CO2 a human could possibly produce while sleeping for 8 or so hours.

I implied about a max of 246 grams of CO2 added to the room per person. For a pretty tiny room 10ftx10ftx10ft you have about 32400 grams of air so you would add about 7500ppm of CO2.

This site claims under 1000ppm indicates good air quality but over 5000 for many hours is needed to feel ill effects from the CO2.

http://www.health.state.mn.us/divs/eh/indoorair/co2/index.html

 

[Tulips]

http://www.epa.gov/iaq/largebldgs/i-beam/text/hvac.html

 

[bigstew123]

All HVAC systems have a damper that allows outside air in. Older systems use a damper with a fixed % opening that closes off if the outside air gets too cold and may freeze the coils in the winter. Modern systems use Co2 sensors, many built into the thermostats, that regulate the amt of fresh air intake. All schools in my district use these sensors. I worked there for a few years, and we could see the Co2 levels spike when the kids came into the classrooms. The HVAC would run continuously during the day with the heat or cooling coils turning on and off as needed, and the outside air damper exchanging the air as necessary. Hope this answer is helpful.

 

[QuantumPion]

Water is significantly heavier than air so something that is rated "waterproof" must withstand a lot more pressure than something that is "airtight."

Thus the reason waterproof rating is based on meter depth, which roughly translates to pressure.

Wow, that's a lot of science fail there.

 

[Nova Web]

Air conditioning does not consume the oxygen in the mix. The air blown in has the same ammount of oxygen as it enters the conditioning unit.

 

[WHAMPOM]

Hi all,

I always wonder how the hotel rooms get oxygen in the rooms that people don't suffocated? They sealed te doors and windows, the air condition in there does not have intake pipe from outside like the first time window unit that have options you can turn on fresh air or recycle air like the car aircondition.

Does those aircondition regenerate oxygen? I hope some engineer can coming and provide an answer.
Thank you.

'cause central heating/cooling uses a heat exchanger using hot/cold exhaust air to warm/cool fresh outside air.
And healthy air requires so many full exchanges an hour.

 

[Red Squirrel]

Even if there was no hvac at all a building as a whole would still have oxygen come in from doors/windows being opened throughout the day. They are also not perfectly sealed, though if you want proper efficient construction it should be perfectly sealed so you don't want to count on that for oxygen. Normally a big building will have quite large HVAC units to exchange air even if individual rooms don't. i would imagine they would also use HRVs to be more efficient. They pass the air through fins to try to keep the indoor climate in, while changing the actual air. The fins act as a heat exchanger so the hot air exiting the building touches the fins and the cold air entering touches the same fins on the other side. They are interweaved so every second fin is intake and other is exhaust. so 2 pipes go outside and 2 pipes go inside.

Buildings like hospitals and such have quite robust HVAC systems too, as some rooms will actually have negative pressure so that any contaminates don't enter the other rooms. When you walk in the hospital here you can actually hear a whistling sound as the door closes behind you since the air is rushing in. In that case they probably don't really care about efficiency, only sanitation.

 

[who?]

https://reepgreen.ca/2016/03/breathe-fresh-air-air-tight-house/