OT: humid air - less comfortable and less dense?

Hi,

I have a FFM and have found that when the relative humidity is 70% and higher, it's harder to breathe with the mask. (During the spring when the relative humidity was at 50%, I found I could leave the humidifier tank dry and the air was comfortable.) I have seen some posts mentioning solutions being AC and dehumidifiers. Those ideas make sense.

Is humid air less dense or more dense than dry air? It sure feels more dense to me.

I read in one post and also in a tabloid paper today that humid air is less dense because the molecular weight of water is lower than other molecules that are typically in the air. Without mentioning the ideal gas law and the relationships described by PV=nRT, I think the article referred to this notion that the number of molecules must be conserved in the air such that if water vapor is present, that means other components of air that are of higher molecular weight are "driven off."

Right there, that seems to support the notion that the atmosphere is not a closed system. If I recall, the ideal gas law only applies to a closed system. The local weather conditions involve higher and lower air pressures and variable temperatures intra-day and seasonally. There are plenty of external factors influencing temperature and pressure, and I don't think it can be said that a region's atmosphere can be considered a closed system.

One post mentions that clouds formed of water vapor are less dense than surrounding air, which is the reason clouds are high in the sky. Fog is also water vapor, however, but it is low to the ground.

Looking for enlightenment. Thanks.

InsomniacGuy wrote:One post mentions that clouds formed of water vapor are less dense than surrounding air, which is the reason clouds are high in the sky. Fog is also water vapor, however, but it is low to the ground.

Looking for enlightenment. Thanks.

well, according to the BBC, clouds are heavy, form in the sky, and usually evaporate before they reach the ground.

https://www.youtube.com/watch?v=M-FRLq5pAho

InsomniacGuy wrote:Hi,

I have a FFM and have found that when the relative humidity is 70% and higher, it's harder to breathe with the mask. I have seen some posts mentioning solutions being AC and dehumidifiers. Those ideas make sense and seem to encompass the possible solutions.

I read in one post and also in a tabloid paper today that humid air is less dense because the molecular weight of water is lower than other molecules that are typically in the air. Without mentioning the ideal gas law and the relationships described by PV=nRT, I think the article referred to this notion that the number of molecules must be conserved in the air such that if water vapor is present, that means other components of air that are of higher molecular weight are "driven off."

Right there, that seems to support the notion that the atmosphere is not a closed system. If I recall, the ideal gas law only applies to a closed system. The local weather conditions involve higher and lower air pressures and variable temperatures intra-day and seasonally. There are plenty of external factors influencing temperature and pressure, and I don't think it can be said that a region's atmosphere can be considered a closed system.

One post mentions that clouds formed of water vapor are less dense than surrounding air, which is the reason clouds are high in the sky. Fog is also water vapor, however, but it is low to the ground.

Looking for enlightenment. Thanks.

Is there a question in there somewhere?
I really can't tell where you're going with that.
This therapy is different for everybody, their humidity needs can vary for any number of reasons, seasons and other factors.

I live in a relatively high, dry, mountainous area and use "passover" (cool) humidity year round. The dry air flowing over the water in my HH tank and picks up some humidity. I find it to be just about right for me to keep my nasal passages open, but others may not find that it suits them.


Den

.

Absent visible vapor droplets, humid air is less dense than dry air.
Fog stays close to the ground because the air in which fog forms is colder and therefore heavier (denser) than warmer air above it.

I suspect, my own speculation, that clouds stay elevated because they are less dense than the air below them. The air is not a single uniform gas but in the atmosphere can be highly stratified as shown from an airplane when it is clear at ground level and up quite a ways, then intensely cloudy for some more distance, and finally clear to the upper limits of the atmosphere.

BTW, for any mixture of oxygen, nitrogen, carbon dioxide, and water vapor (normal air that we breathe), increasing the percentage of any of these reduces the percentages of the others. I don't think that increasing the relative humidity will make any significant difference in the amount of oxygen in the mixture. So set the humidity level to that which is comfortable for you and move on to other concerns.

Everyone has their happy moisture settings. I use a nose mask, and leave my "heat" setting on 4. During humid months, it doesn't use much water. During dry winter months, the reservoir is nearly out of water in the morning. It is just humid air doesn't pick up much moisture from the tank.

Height of clouds..... give me the temperature, and visible clouds, I'll give you the dew point. Air cools as it rises, once it cools enough for the moisture content to form those nice cumulus clouds you know air temp has reached the dew point. So with Texas being 95F, those clouds on a humid day are around 5,000 ft. On a really dry day they form at 12,000 feet. Good stuff to know when flying. (Tip, July/August in Texas look out for afternoon thunderstorms).

Humidity... height of the clouds, gives me the dew point. It also tells me how much runway I'll need. Cool dry day, fully loaded, my little plane is happy with 700 ft.
Increase the temp, or increase the humidity, and I may not clear that 5' cow fence at 800'.