If you are concerned about fire, it is prudent to store flammable materials in a fireproof box. If you are in an area prone to flooding, you might consider keeping your film and photographs offsite (perhaps in a bank safe deposit box).
It is preferable to use "archival" quality storage systems. Zip lock bags are not suitable for this purpose. They can also trap moisture.
Use of a dehumidifier should be avoided because they use heat to draw moisture from the air. Heat can accelerate degradation of stored materials. However, it is a good idea to use a desiccant, such as silica gel packs. To ensure that they continue to work, you should periodically replace or regenerate them. You can regenerate them by heating them for a few minutes. Let them cool before reuse.