Thermal safety in lithium-ion batteries is a critical aspect due to their increasing use in energy storage systems and electric vehicles. To investigate thermal abuse conditions, numerous studies employ specialized equipment to accurately measure physical variables during thermal runaway events. However, such tests typically require robust equipment which limit their availability in conventional laboratory environments. In this context, the present study proposes and evaluates an experimental methodology based on the use of a climate chamber combined with an instrumented reduced-volume container, to reproduce severe external heating conditions. The thermal behavior and gas emissions associated with thermal runaway events were characterized in six cylindrical lithium-ion batteries of two different chemistries. Six cylindrical cells with NMC and NCA cathode chemistries were subjected to thermal abuse tests. In addition, gaseous emissions and mass loss were quantified after the event. Based on these tests, the results showed that NMC cells reached a higher average maximum surface temperature of 1086°C, whereas NCA cells exhibited the highest pressure values, with an average of 24.64 bar. Gas emissions presented high concentrations of CO and CO₂, reaching values of up to 381,555 ppm. Furthermore, both chemistries experienced a mass loss exceeding 50% after the test. Overall, the results indicate that both cell types exhibit similar behavior in terms of gas emissions, while NMC cells show greater thermal severity during the exothermic event. This work demonstrates that a system based on a climate chamber combined with an instrumented container is capable of reproducing severe thermal runaway conditions comparable to those achieved in specialized abuse-testing facilities, enabling the simultaneous characterization of temperature, pressure, and gas emissions in lithium-ion cells.