Few safety questions come up as often among homeowners and facility managers as this one: how many fire extinguishers do I need? What Determines How Many Fire Extinguishers You Need in a Building? Residential and commercial properties answer the question of how many fire extinguishers do I need quite differently. When working out how many fire extinguishers do I need, floor area, building layout, hazard classification, occupancy type, and code-mandated travel distances all shape the final count. NFPA 10 sets maximum travel distances, minimum ratings by hazard class, mounting heights, and inspection intervals, serving as the benchmark that most local codes and insurers follow.