Most safes may be designed to protect your belongings and important documents from fire and theft, but chances are they aren't waterproof. Even if you don't suffer from flood damage, moisture can still infiltrate your safe, especially if you store it in a damp location. That moisture can lead to mold and mildew damage of the items you are trying to store and protect. There are several ways you can absorb the moisture inside the safe, keeping your items protected from damage.
Lay silica gel packets inside your safe. Silica gel packets, which you can find in craft and hobby stores, are a desiccant that absorbs moisture and can be used over and over again. Remove your silica gel packets once a year and dry them in the sun for four to six hours before returning them to your safe.
Pour 1/2 cup of dry rice into a jar and place the open jar in the safe. Rice absorbs moisture and it doesn't contain any harmful chemicals. Replace the rice in your safe every four to six months to maintain dryness within the safe.
Open a box of baking soda and place it within the safe. Sodium bicarbonate (baking soda) absorbs moisture and deodorizes, an added benefit if you are also trying to eliminate the odor of mildew from prior dampness.
Purchase a calcium chloride crystal moisture absorber such as DampRid or Moisture Absorbent. Calcium chloride crystals draw moisture out of the air and into the crystals, drying out your damp safe. These types of moisture absorbers can be found in the cleaning supply section of most grocery stores.
Place two to three moth balls in a cup or bowl and set it inside the safe. Moth balls are known to absorb moisture, but also they exude chemical fumes that may be harmful when ingested. Wash your hands thoroughly after handling to avoid accidental ingestion. Unfortunately, some items in your safe may absorb the moth ball odor, which many find offensive.