Gun room humidity level

**carrguy1** · June 15th, 2020, 06:04 PM

I did some searching both here and on Google but I figured some here may have more opinions or experience. Several years back I had my guns in a gun cabinet at my old house and used one of those reusable silica dehumidifiers, the kind you plug in when the beads change color to dry them out. That worked fine as the cabinet was a small enclosed space. I have since moved and outgrown the cabinet so about a year and a half ago I built a gun room in my basement.

The basement itself is comfortable as long as I run my 70 pint dehumidifier. In the summer I sometimes have to empty it twice a day but usually once is enough. I also have a 50 pint unit as backup someone gave me that I will sometimes use in combination if I feel the humidity is too high or if I forgot to empty the other one for too long and level has gone up. When I built the gun room I put a temperature and humidity sensor in there and the receiver is in the main basement so I can monitor the temperature and humidity both in the main basement and in the room. With the dehumidifier running in the basement the humidity hangs around the high 30% level. The gun room has two of the reusable silica dehumidifiers and a small Eva Dry dehumidifier that uses Peltier effect to collect moisture. The tank is maybe a cup or two and will fill in a couple of days. With these 3 devices and the bigger dehumidifier running in the main basement the humidity will hang in the upper 40% range. The basement temp is in the 70s in the summer and 60s in the winter. The gun room averages about 5-10 degrees cooler.

I thought I had read somewhere that metal will begin to rust at 55% humidity so I’ve always been a little concerned about the upper 40% range the gun room normally sits at. I decided over the weekend to put the 50 pint dehumidifier in the gun room. After a day the humidity was low 30s but temperature climbed to low 80s. It felt like a heater was on in there. Then I was concerned low humidity and warm temps wouldn't be good either for fear of drying out stocks and leather slings. The problem with the 50 pint unit is it never shuts off even on auto. Apparently that’s just how that model works. The fan always runs but the compressor cycles on and off as needed. It only truly shuts off when the tank is full. So I put it on a timer. Right now I have it running for about an hour every other hour. So on an hour, off an hour. Temp is now low to mid 70s and humidity is mid to high 30s. I may reduce the run time further.

I just now searched Google though and found reports that iron will begin to rust above 50% and steel above 80%. So if you’re still reading I’m just wondering what your thoughts or experiences are with anything like this. Reduce the run time of the 50 pint unit further or pull it out of the gun room altogether leaving the small devices I have in there where it’ll go back to being around 45-47% humidity and 10 degrees cooler than the main basement?

**West Chester** · June 15th, 2020, 08:12 PM

I keep my room at about 45% and never an issue. I use Kasa wifi outlets so can turn on and off a dehumidifier from my cell phone

**carrguy1** · June 16th, 2020, 09:37 AM

Originally Posted by West Chester

I keep my room at about 45% and never an issue. I use Kasa wifi outlets so can turn on and off a dehumidifier from my cell phone

Smart outlets are an idea but if I already have a timer that works for what I want I*m fine with that. I reduced the run time for each iteration it turns on yesterday so we*ll se what that does today. It*s the kind of timer where you just push down or pull up the little tabs on the dial for when and how long you want it to run. I guess 45% would be fine if it would stay there consistently with the three small devices I had. In the winter it stays below that but in the summer it sits at 47-48% which I just feel is a tad too high and if the 70 pint in the main basement fills and I forget to empty it the gun room can easily climb over 50% and that*s not enough margin of error for me. I don*t have a sump pump in my basement but I do have a laundry sink. I just never got around building a set up for the dehumidifier to sit above it and drain into it. It*s a high sink, about chest level, so that*s a little inconvenient.

**bug** · June 16th, 2020, 10:05 AM

There are small (50cal ammo can size) portable sump pumps available that would get your condensate to the stationary tub. Also, why is the gunroom 10 F cooler than the basement? I'm sure you know that %RH is temperature dependent. Ideally, the GR and the basement should be the same temp/RH. That way, when you open the door you don't introduce warmer possibly moist air to the room. Do you have any air supply to the gun room other than the door?

Bob D

**Hodgie** · June 16th, 2020, 11:14 AM

The NRA Firearms Museum recommendation is 65-70 degrees Fahrenheit, and 45% to 50% humidity. This should be a year-round constant, not an average.

**ShooterInPA1** · June 16th, 2020, 11:18 AM

Per NRA, the ideal "museum arms" conditions for gun storage are 50% humidity at 70 degrees.

**Ronin** · June 16th, 2020, 12:04 PM

Originally Posted by carrguy1

I decided over the weekend to put the 50 pint dehumidifier in the gun room. After a day the humidity was low 30s but temperature climbed to low 80s. It felt like a heater was on in there. Then I was concerned low humidity and warm temps wouldn't be good either for fear of drying out stocks and leather slings.

Dehumidifiers put out warm air by design. That's why your smaller, enclosed, room went up to 80 degrees.

**carrguy1** · June 16th, 2020, 09:10 PM

Originally Posted by bug

...why is the gunroom 10 F cooler than the basement? I'm sure you know that %RH is temperature dependent. Ideally, the GR and the basement should be the same temp/RH. That way, when you open the door you don't introduce warmer possibly moist air to the room. Do you have any air supply to the gun room other than the door?

Bob D

So a little more background here. The previous owner used the room as a dark room for photography film development, old school. I modified it a lot but it*s still fairly sealed up. I did Drylock (Drylock Extreme to be exact on cinder block walls) the whole basement when I was fixing and cleaning things up down there and then the gun room when I was doing that. I did this to hopefully cut down on the moisture that comes through the walls and because white walls look a lot nicer than how They used to look. So because the room is fairly sealed the temp and humidity coming through the exterior walls builds up slightly differently in there. I understand that temp and RH would ideally be the same inside and out and I*ve toyed with the idea of putting a louver vent in to allow for more ventilation but haven*t gotten around to it. The air outside the room going in when I open the door may be warmer but it*s definitely dryer.

Originally Posted by Hodgie

The NRA Firearms Museum recommendation is 65-70 degrees Fahrenheit, and 45% to 50% humidity. This should be a year-round constant, not an average.

Originally Posted by ShooterInPA1

Per NRA, the ideal "museum arms" conditions for gun storage are 50% humidity at 70 degrees.

This is good information. I appreciate it. That*s about where it sat before I put the 50 pint unit in there. Consistently 65-70 degrees and around 47% humidity so maybe it was already just fine.

Originally Posted by Ronin

Dehumidifiers put out warm air by design. That's why your smaller, enclosed, room went up to 80 degrees.

I figured as much. The weird thing is the air blowing out of the dehumidifier feels cool to my hand, cooler than the room temp anyway.

I*ve been trying to fine tune the timer and I*m sitting around 73 degrees and 38% humidity so I may keep playing with it to see what happens. I can always just go back to the small Peltier dehumidifier (https://www.amazon.com/dp/B000H0ZDD2..._P0w6EbKY65CZ3) and the reusable desiccants which sounds like it may have been a fine setup after all.