Fire is commonly described as a chemical reaction between fuel and oxygen, yet this framing obscures why combustion is abundant on Earth, rare elsewhere, and especially destructive to biological matter. This mini paper reframes fire as a resonance-driven collapse of biological geometry within USP Field Theory. Living structures are treated as slow, hand-assembled resonance configurations operating within a bounded mismatch corridor (Δf). Fire occurs when external forcing pushes this geometry beyond a critical threshold, allowing oxygen to act as a rapid relaxation channel that resets biological ordering toward inorganic equilibrium. The interpretation is compatible with standard thermochemistry while offering a geometric, field-level picture of ignition, threshold behavior, and runaway combustion.