Here's why:
* Common noun: It refers to a general category of things rather than a specific one. It doesn't refer to a particular fire, just the concept of fire in general.
* Concrete noun: Fire is a tangible thing that can be seen, touched (with caution!), and experienced.
It's also worth noting that "fire" can be used in a more abstract way, such as "the fire of passion" or "the fire of ambition." In these instances, "fire" would be considered a metaphorical noun, representing an intangible concept.