Unlike nitrate, safety film is not a fire hazard.
There are several considerations when storing negatives. First is the environment. Negative deterioration is slowed when the material is stored at a constant temperature and humidity.
The second consideration is that negatives range in size. Each size needs to be stored separately so that the weight is evenly distributed.
As with all photographic material, wear non-latex disposable examination gloves when handling the negatives.
Storage recommendations for negatives as well as Frequently Asked Questions can all be found in Preserving Your Family Photographs. Or if you have questions, please feel free to email me at firstname.lastname@example.org.