This thesis addresses the critical issue of gas crossover in small gap alkaline electrolysers, significantly impacting the safety of hydrogen production systems. The research aims to optimize electrolysis cell design by investigating how bubble coverage, gap size, and electrolyte flow influence hydrogen crossover, particularly for integration with renewable energy sources. Computational simulations using Ansys Fluent revealed that higher bubble coverage and controlled electrolyte flow significantly reduce crossover rates, ensuring safe Hydrogen-to-Oxygen levels. The study highlights the delicate balance required between minimizing gap size and managing crossover risks. Additionally, the research validates numerical results with an analytical model, providing a robust predictive tool for practical applications. The findings offer valuable insights and practical recommendations for the design and operation of alkaline electrolysis systems, enhancing their safety for industrial applications. This work supports global efforts to reduce greenhouse gas emissions, facilitate the transition to renewable energy sources, and advance the hydrogen industry, which is pivotal in the evolving energy landscape.