Why Won't Humidifiers Raise Lab Humidity?

[daviddoria]

Everyone in my office (8.5 x 3.5 x 6 meters) was complaining of dry eyes/throat. We thought "hey we should check the humidity". We bought two separate humidistat's that both read 15% RH at 73 degrees F! So we bought a humidifier. Just one of the small ones that holds 2.2 gallons and empties it every 12 hours. We ran it constantly for several days with absolutely no increase in the humidity level. So I brought the same kind of thing in from home that I had, and we ran both constantly for several days. Again, no change. We thought it may have had something to do with the AC being on, so we turned it off for a few hours and still no change.

I am in Albany NY, so its cold out (~20 degrees F), but that doesn't seem like any kind of INSANE temperature which would cause this big of a problem.

Is there anything we can do to fix this??

Thanks!

David

 

[Danger]

Do you, by chance, have any dessicant materials in your lab, such as silica gel? I'm only asking because I can't think of any other reason why a functional humidifier is having no effect. My first thought is that something might be absorbing the extra moisture.

 

[daviddoria]

no, its a computer vision lab so there are no chemicals or anything, just 4 computers, a refrigerator and now a humidifier...

We were just thinking there was some crazy amount of airflow or something if it was designed to be more of a real lab? Is there some way to easily test this theory? Or a better way to raise the humidity?

Thanks,

Dave

 

[Danger]

Unfortunately, that was my best shot. Russ Watters, on the other hand, is an expert in things involving air conditioning, humidifying, and other air-related issues. He should weigh in shortly.

 

[russ_watters]

It is winter. When the air is cold, it holds less moisture. The [absolute] humidity of outdoor air in winter is pretty close to zero, so the [relative and absolute] humidity inside, even with people breathing is also going to be pretty close to zero. Partial pressure of water vapor is a regular pressure, so any humidity inside is going to get sucked out of the building. It requires a lot of humidification to make a space humid.

A humidifier like the one you bought does wonders for my bedroom, but is wholly unsuitable for a lab. Your biggest problem is likely that since it is a lab, you have a high ventilation rate. That means your lab is exchanging its air with outside air. Since the air being brought in has almost no humidity, it takes an enormous amount to noticeably increase the humidity.

You can talk to your facilities department about getting a humidifier installed in your HVAC system, but unless you have a specific lab-related reason for it, they are not likely to be willing to take the expense.

If you are curious, you can google psychrometrics and the psychrometric chart for the actual numbers. Right now outside my house, it is 30 F and 68% rh, a pretty warm and humid winter night. At equilibrium, that corresponds to 15% humidity at 70F inside.

[edit] Here's a psych chart: http://truetex.com/psychrometric_chart.gif
The way it works is that you find your outside temperature along the bottom and trace up vertically until you get to your relative humidity curve for the outside air (humidity is available via the national weather service). Then you trace horizontally until you get to your indoor temperature. Then read the corresponding indoor relative humidity at that point.

 

[jingles]

I agree with Russ that you problem is most likely one of air exchange. I live in an apartement in Edmonton and the lack of humidity is brutal in the winter. Also I live on the 17th floor and feel that this adds to the probelm. I was unable to get any improvement with the humidifier until I blocked off the return vents. This decreased the amount of air exchange in the apartment and increased the humidity.

 

[daviddoria]

Is there any harm in partially/mostly blocking the return vent?

 

[jingles]

In my apartment I have hotwater radiant heat. If the lab has forced air heating then this would probably be affected. It might be something you can play with though.