For home storage, a fireproof box can be a sensible choice if fire is your main concern, and offsite storage may be worth considering in flood-prone areas. For the photos and slides themselves, use archival-quality storage materials rather than ordinary plastic bags.

Zip-lock bags are not recommended for long-term photo or film storage. They are not archival, and they can trap moisture, which may make problems worse.

A heat-based dehumidifier inside a storage box is also not ideal, because added heat can speed up deterioration of photographic materials. A better approach is to use desiccants such as silica gel packs to help lower humidity in a closed container. Just make sure to replace or regenerate the packs periodically so they remain effective.

In short: use archival storage, avoid zip-lock bags, avoid heat-producing dehumidifiers, and use rechargeable silica gel or similar desiccants if you want extra humidity control.