Winters here in AK are very dry. I have an 18x22 room with gun safes, ammo etc in it. The room sits at around 20% humidity. I bought a room humidifier from home depot and it goes through a gallon of distilled water every two days but the humidity only climbs to 22-24% max. The room is sealed very tight. Radiant floor heating but there is an HRV system that runs every morning dumping in dry fresh air.

I'd like to increase the humidity to 30-35% at least in the gun safes (Liberty 64s). Since the safes are closed most of the time I dont think the room humidifier helps them any.

Short of funneling steam into the inside of my safes, does anyone have any suggestions?

Would it be wise to block the HRV vent?

I've also got a 12x18 vault under seemingly never ending construction that is going to have the same issue.

I can't seem to find an easy way to install a whole house humidifer. We have no vents except the HRV. House is entirely radiant in floor heat and no AC system.

Why do you want humidity in your gun safe? Most people buy things to remove moisture from inside their gun safes.

Satire?

Dry is better.

is this supposed to be ironic

No its not a joke.

20% humidity is too low and bad for things... like wood stocks, leather, cardboard etc

I hear a steamed salt water solution can be particularly effective for preserving your valuable cardboard collection...
Rather than risking a rusty mess, why not simply spend one day a year oiling your wood stocks and leather accessories?  Serious question...

Well lets look at what would go in a safe,

Metal, the dryer the better. I treat the outside of my guns with Birchwood Casey Barricade, and they stay in like new condition.

Wood( Like a rifle stock) Is either sealed or oil finished. so if the stock is able to take in moisture it will swell.

Leather, leather doesn't get stored in a safe. Again it should be treated with a product such as the stuff Galco sells to keep it conditioned.
Also stay away from products like saddle soap , they will soften and weaken leather over time.

Ammo, ammo should never be stored in a gun vault. In case of fire the safe will contain ammo pressure to a point and then the vault will explode. So it's like having a atomic bomb in your gun room.

So short story is the dryer , the better. I cringe when people even talk about putting a humidifer in the same room as the vault.

Now if you don't belive me, do some searching and many people put their vault in the basement and there are numerous horror stories of rust on the internet.

IMHO, you're FOS.

A safe will not explode if it has ammo in it during a fire. Wood permitted to dry too much will crack. You don't store any leather in your safe? Lol...

OP, I  would be very cautious putting a humidifier in a sealed safe...

Regarding the humidifier in the room, if you have a system cycling out the air for fresh air that's your problem. Your humidifier spends all that ti.e putting humidity in the air then you exchange it for cold dry outside air...

I understand the potential concern, but I live in Phoenix and never heard of anyone intentionally humidifying their house for collectibles.  I have heard of people installing a humidifier for comfort reasons.  You would need something like this:

https://www.homedepot.com/p/Hamilton-Whole-House-Furnace-Mount-Flow-Through-Humidifier-12HF/202771119

If it was 20% non stop humidity, but as long as its broken up more humid periods, maybe not so bad for wood.

Can you control the HRV rate? On ours I can do down there and dial duration up or down.  Is that HRV just dedicated to the single room?

As to getting more humidity into the safes, about the only thing I can think of is either hole sawing an opening into the back, and mounting a computer fan there, or possibly running a couple of slots low, and a couple more high, again on the back wall of the safe. Of course, you're compromising fire ratings....

Other than running the HRV less, doing some kind of swamp cooler style humidifier, adding plants, or an aquarium, can't think of anything else. I'm running 22% humidity inside right now, -11 outside and 53%.  But all my stuff indoors is synthetic, I don't know what will happen when I bring all the wood stocked stuff up and accessories.

Toss a 58% Boveda pack in there and call it a day if it makes you feel better.

Stop being a fudd with all your dang wood and your leather and such!

If low humidity was that bad on gun stocks wouldn't all guns out west have cracked stocks? You can buy some humidity balls on Amazon, which wouldn't increase the humidity to much. It's a ceramic ball in a little dish with water in it. The ball soaks up the water and releases it in the air raising the humidity slightly. It's for use in a room, don't think i would put it inside a safe though.

There are plenty of stocks with cracks in them... can you provide evidence that it isn't due to humidity shrink?

Humidity shrink is a well-known problem in the "wood" industry. There is no evidence the gun industry is immune from it...

I'm below 20% out west and I've never had a problem with stocks cracking.
I would rather see a replaceable stock than rust.
Unless it's a collectors item.