Structure fires in the random game:
The adventure game doesn't have structure fires unless YOU start them (fire arrows). The Random Island game, however, will occationally cause one of your structure to catch on fire. During my gameplay, these fires have only occured to three of my structure types (so far); my Shelter, Tent, and (small) storage buildings. These structure types have repeatedly caught on fire, but none of my other structures have. I'm not sure if other building types are immune or just have less chance of fire. Although you can put out a fire in a tent by packing it away in your inventory, I have discovered no way of putting out fire in other buildings. If a storage unit is destroyed by fire, all items that were stored inside will remain behind on the ground where it was located.