<p>In Constant Volume Combustion (CVC) and wider combustion applications, unwanted transitions to detonation can occur in highly reactive end-gas with a reactivity gradient present. The objective of this present study was to identify variables encountered in practical applications which influence detonation transition behavior. Different temperature gradients were imposed on stoichiometric H₂/C₁₀H₂₂/O₂/Ar mixtures with a 5% H₂ fuel mass percentage in a closed optical vessel through varying the temperature of heating cartridges placed at the top, middle and bottom of the chamber. In Part 1 of this study, ultra-high-speed schlieren records were analyzed to identify the exact mechanism by which detonation transition occurred for a mixture initially at 3 bar with top, middle and bottom heating cartridge temperatures of 453 K, 455 K and 441 K respectively. At this reference temperature gradient, both a vertically and laterally propagating autoignition wave would form. Zones with a reactivity high enough to transition to detonation would form at the intersection of the two waves as well as at the end wall due to the effects of reflecting pressure waves. Part 2 of this study analysed the effects of varying temperature gradient. A stronger temperature gradient condition resulted in end-gas with insufficient reactivity to transition to detonation. A weaker temperature gradient resulted in the development of more zones with sufficient reactivity to transition to detonation when compared to the reference temperature gradient. Although temperature gradient was the ultimate determinant of detonation transition behavior, it was found that changing chamber geometry could work towards suppressing detonations in borderline cases.</p>