Hydrogen transportation poses significant explosion risks, especially under confined conditions. This study evaluates the accuracy of the Conservation Element/Solution Element (CESE) method, with finite-rate chemistry, for predicting blast loads from confined hydrogen–air detonations at varying initial compositions. A shock tube simulation is compared against one-dimensional theory at the detonation front, using four reaction mechanisms (7 to 19 species). The 7-species mechanism predicts the Chapman–Jouguet (CJ) state within 1%–2% error up to 40 vol% H2, offering a computationally efficient option for large simulations, considering that computational time scales with the square of the number of species. While mesh refinement (0.2–2 mm) improves peak pressure prediction, impulse remains 5% underestimated due to the unresolved induction zone. The proposed 2D model – using 7 species, 1 mm mesh size and inviscid flow – is then validated against a confined detonation experiment from literature. It accurately predicts detonation speed, pressure history (including shock reflections), and impulse along the 3-metre chamber. The study provides insight into the applicability and limitations of the CESE-chemistry method in confined detonation scenarios.