We suspect that there may be mold in our home (as previously discussed here on AnswerPool), and we borrowed a dehumidifier from a friend to see how much moisture it would take out of the air. I put it in my bedroom and ran it for about 5 hours, and it produced 7 cups of water! It's a rather large floor model, but even so, I'm concerned that 7 cups is an awful lot of moisture in such a short period of time.

I did some searching online, and couldn't seem to find any information on how much moisture should be in the air or how much water is normal for a dehumidifier to pull out. Does anyone know if this is an abnormally large amount of moisture or where I can find out? Thanks!

"Normal" depends on where you live, what season it is, blah. For instance down south in the swamp lands normal humidity is around 100% nearly all the time, but in the Southwestern states in the dry lands humidity is around or less than 20%.

Virginia is a high humidity area, so I would expect a lot of water being pulled out of the air when running a dehumidifier. I do not know how 7-cups of water in 5 hours translates to humidity percentage in the air.

To measure humidity you need a hygrometer : http://inventors.about.com/library/inventors/blhygrometer.htm


Humidity tends to run higher than outside humidity due to indoor plumbing, cooking and the fact that people just release constant water vapor from every pore and with every breath they release. So humidity in a room will be higher if folk are in it or have been in it for a time, say the bedroom over night.

Now, before I answer this, I must remind you that this answer is in General as I do not know your house or the area you live in. Whether you live in a humid area or dry this time of year.

Humidity is the amount of water in the air at the time given in % relative humidity.

At 70 degs F and 40% humidity, there are 43 grains of water per pound of air. This is rather dry air and humidification is recommended.

Raise that temperature to 80 degs F and the air can now hold up to 61 grains of water per pound of air and still be at 40% humidity.

100% humidity at any temperature would give you heavy fog or even rain. The air is fully saturated and can not hold anymore water.

Can you have rain or snow at a lower humidity? Yes, as this is a function of the humidity at higher elevation. Up in the clouds. I am sure you have heard the statement from you local weatherman. It is raining but the rain is not reaching the ground. This is when the air a lower elevation can hold more water and the air is absorbing the rain before it hits the ground.

I am telling you all this to show what humidity is.

The best way for you, and me, to figure this out is to get a humidistat. This is a gauge the reads percent relative humidity. I can tell more by knowing what the outside air temperature and humidity and you inside temperature and humidity.