A thermodynamically consistent equation of state for &bgr;‐HMX, the stable ambient polymorph of HMX, is developed that fits isothermal compression data and the temperature dependence of the specific heat computed from molecular dynamics. The equation of state is used to assess hot‐spot conditions that would result from hydrodynamic pore collapse in a shock‐to‐detonation transition. The hot‐spot temperature is determined as a function of shock strength by solving two Riemann problems in sequence: first for the velocity and density of the jet formed when the shock overtakes the pore, and second for the stagnation state when the jet impacts the far side of the pore. For a shock pressure below 5 GPa, the stagnation temperature from the jet is below the melt temperature at ambient pressure and hence insufficient for rapid reaction. Consequently, for weak shocks a dissipation mechanism in addition to shock heating is needed to generate hot spots. When the stagnation temperature is sufficiently high for rapid reaction, the shock emanating from the hot spot is computed, assuming a constant volume burn. For initial shocks below 20 GPa, the temperature behind the second shock is below 1000 K and would not propagate a detonation wave. © 2004 American Institute of Physics