HHO gas, which is obtained by the electrolysis of water, is a promising alternative fuel. This paper presents a review of important features and techniques used for producing HHO gas. Various aspects of the thermodynamics and chemical kinetics of electrolysis reactions are discussed. Design and operating parameters for improving the gas production rate are identified. Widely different hypotheses regarding the structure and composition of HHO gas are compared in depth. The state of the art on the use of HHO gas in Internal Combustion (IC) engines is presented in the latter part of the paper. It is seen that the introduction of HHO gas increases engine torque, power and thermal efficiency, while simultaneously reducing the formation of NO_x, CO, HC and CO₂. The major challenges in using HHO gas in engines are identified as system complexity, safety, cost and efficiency of electrolysis.

通过电解水获得的HHO气体是一种有前途的替代燃料。本文介绍了用于生产HHO气体的重要特征和技术。讨论了电解反应的热力学和化学动力学的各个方面。确定了用于提高产气率的设计和操作参数。深入比较了有关HHO气体的结构和组成的各种假设。本文的后半部分介绍了在内燃机（IC）中使用HHO气体的最新技术。可以看出，引入HHO气体可提高发动机扭矩，功率和热效率，同时减少NO _x，CO，HC和CO ₂的形成。。在发动机中使用HHO气体的主要挑战被确定为系统的复杂性，安全性，电解的成本和效率。