Hydrogen is being widely promoted as the future primary energy carrier to replace current hydrocarbon fuels. Governments and industries are investing in research and development programs to develop hydrogen production, transport and storage technologies. In addition, hydrogen gas is currently used in chemical processing and aerospace applications. Hydrogen gas is combustible with a wide flammability range of about 4 to 75 percent, a low ignition energy, and a low gas density. With the expanding application of hydrogen gas coupled with its highly combustible nature, focus must be placed on safety. Detection and monitoring technologies are needed which can provide low limits of detection, high sensitivity, a wide detection range, fast response times and ease of implementation to ensure public safety. Hydrogen sensors are of increasing importance in connection with the development and expanded use of hydrogen gas as an energy carrier and as a chemical reactant. Also they are essential to facilitate the detection of accidental hydrogen releases wherever hydrogen will be produced, distributed, stored, and used. This thesis highlights the importance of hydrogen sensing regarding the safety and reliability. The first chapter describes and classifies the different types of hydrogen sensors and the technology behind them. Characteristic performance parameters of these sensor types, such as measuring range, sensitivity, selectivity and response time are reviewed. In the second chapter the methods of the tests performed on the commercially available hydrogen sensors are described. Parameters such us detection limits and response times are measured and the advantages and disadvantages of those sensors are written down. In the third chapter new hydrogen detecting technologies will be mentioned either available in the market or under development and afterwards we will refer to the improvements of knowledge on hydrogen safety, according to the standards and guidelines of the International Energy Agency's Hydrogen Implementing Agreement. Regulations will be also mentioned. The fourth chapter describes the framework of the Hydrogen Safety Engineering (H2SE) profession which is defined as an application of scientific and engineering principles to the protection of life, property and environment from adverse effects of incidents/accidents involving hydrogen. Finally a reliable and comprehensive safety risk analysis model has been developed. In the fifth chapter of this thesis there is a summary with the conclusions deducted of this work.