How to Keep Moisture Out of Your Gun Safe

Many new home or gun safe owners don’t think about the need to control the humidity inside of a safe. After all, it’s just a secure box for your guns, right? Why would you need to worry about moisture? Well, most of the US population lives in areas with above 50% average humidity. If your home or apartment’s climate-control system helps dry the air, that’s all well and good. But many don’t.

Additionally, temperature changes, weather patterns, or low air circulation in the safe can contribute to humid conditions. As we explain in our article about the proper care and storage of firearms, maintaining an appropriate level of humidity inside your safe (not too humid and not too dry) is one of the main factors that help prevent damage from rust, corrosion, mildew, and mold that can destroy your firearms, valuables, documents, and records.

There are several ways to keep humidity levels appropriately low inside a gun safe, so let’s go over the main options so you can make an informed decision that’s right for you and your situation.

So, for the best compromise for storing both firearms and documents or other vital records in your safe, we’d err on the side closer to 30% humidity if possible, as excess humidity in enclosed spaces can accelerate corrosion and mold growth and just recommend you keep your safe in the coolest place that’s practical and secure in your home.

Remember, too dry is not ideal, either

You may be tempted to get the air inside your safe as dry as possible, but this is not a good idea, particularly if your firearms have wood, laminate, ivory, or bone stocks. If the air is too dry, these materials can shrink, crack, and warp, causing expensive or irreversible damage. Paper records, books, collectible currency, or essential documents inside your safe also need an appropriate humidity level to prevent drying and cracking. You wouldn’t necessarily think that paper items need a certain amount of humidity to prevent damage, but it’s a fact.

Condensation can add moisture to the inside of your safe

Another contributing factor to excess humidity inside your safe can be temperature changes, whether in the environment around your safe, or by bringing cold, steel firearms into a warm room/safe after being outside in cold weather. An uncased, cold gun will often collect condensation, which can accelerate rust. That’s one problem. But suppose you put that dew-covered gun into your safe before it dries out and normalizes in temperature. In that case, that condensation can evaporate into the air inside your safe, and any liquid drops of water can saturate the floor or carpet inside your safe, raising the humidity levels.

Some experts recommend that guns that have been outside in the cold and then brought inside into a warm space should be left in their gun cases until they gradually come up to room temperature. Other experts worry that padded cases or "gun rugs" can absorb moisture and accelerate rust. They might advise you to immediately remove cold guns from soft cases and examine them carefully for signs of moisture. After they have come up to a stable temperature, wipe any condensation off with a soft, dry cloth (be sure to check below the stock line), and apply your choice of rust preventative before placing them inside your safe.

The Dry Rod Dehumidifiers heat to a touch-safe surface temperature of around 100-120 degrees Fahrenheit. This heat creates a natural convection that slowly circulates warm, dry air throughout the safe on a 24-hour basis. This increases the temperature of the air inside to several degrees above the ambient outside temperature. Expansion of the slightly warmer air forces the moist air outside through the small openings around the safe door, leaving the drier air inside. This type of dehumidifier is most effective when mounted horizontally on the bottom of the safe, but it can also be mounted against an interior safe wall.

If your safe is in a location without electrical power access, silica gel desiccants can be appropriate for keeping humidity at bay. However, since silica gel beads eventually become saturated, they only work for so long before they must be renewed or replaced. This means that if you don’t have the ability or desire to check on your safe’s condition frequently, this dehumidification strategy is probably not the best choice for you.

Again, whether you utilize an electric or chemical dehumidifier approach, you must regularly check the humidity levels in your safe to know whether you need to work toward drier or more humid air to stay within that golden 30%-50% zone.

It’s important to note that any water absorbed by rice does not stay in the grains forever. Rice can also lose water, making the surrounding objects more humid, a process known as water desorption (the opposite of absorption). This desorption happens because water vapor always seeks pressure equilibrium, with its molecules migrating from a high-pressure environment to a lower one until stasis is maintained. When an open container of dry rice is placed in a humid room, the rice will exchange water with the air until the vapor pressure in the air becomes equal to the vapor pressure in the rice grains. However, you’d need to use a LOT of rice to dehumidify a room. Probably more than is practical to use unless you’re in the grain storage warehouse business.

In a small, enclosed area like a bucket of flour, a drawer, a box of electronics, or a similar space, a breathable packet of rice can help keep humidity at bay. However, like silica gel desiccants, dry rice only absorbs as much humidity as possible to reach its vapor pressure limit. Then it stops “dehumidifying” and must be dried out in a low oven. Bugs are another potential downside when using rice in a gun safe. Rice is highly edible, and the starch in rice grains can quickly attract all kinds of insects and nasty critters, which you definitely don’t want in your gun safe around the carpet, wood stocks, or valuable documents and photos, which are also tasty starches that silverfish and other creatures crave. For this reason, we usually recommend against using rice inside a safe. If you try rice as a desiccant, monitor it regularly and use an in-safe hygrometer to ensure it’s doing its job.

Finally, if you’re the kind of person who walks around your house turning off all the light switches to save energy and money, running a lightbulb in your safe 24/7/365 might make the corner of your eye twitch. A dry rod dehumidifier uses less energy than most standard incandescent light bulbs. It is specifically designed to create the proper heat level for adequate air circulation and remove humidity inside your safe without the undesirable downside of potentially damaging the finish of valuable oil-finished stocks or essential photos and documents through light exposure.