Control humidity inside safes
Fire safes are often lined with board that holds moisture, and sealed boxes trap damp. Rust, mould and corrosion can ruin documents, metals and firearms.
How
- Put a battery hygrometer inside each safe. Dean Safe suggests aiming for about 50 percent relative humidity. The US National Archives advises keeping papers below 65 percent to stop mould, but not below 15 percent, which makes paper brittle.
- Use a rechargeable desiccant canister in small safes, or an electric dehumidifier rod sized to the safe volume. Dean Safe gives rod lengths by volume: 12 inch under 20 cubic feet, 16 inch for 23 to 30, 18 inch over 35.
- A rod needs a cord path. Only use the maker's knock-out or an approved hole, and never drill a fire safe yourself, as it may break its fire seal or rating.
- Avoid garages, sheds, laundries and bathrooms where temperature swings cause condensation.
- Store papers in acid-free folders and seal important items in waterproof bags inside the safe.
Do these first
Sources
- Moisture, Humidity and Gun Safes. Dean Safe Company, accessed 2026-11
- Storing family papers. US National Archives and Records Administration, accessed 2026-11
- Protecting your important documents and cash (Consumer News, September 2021). US Federal Deposit Insurance Corporation (FDIC), accessed 2026-11