As the world is in need of more sustainable energy sources, the use of new gases like hydrogen or bio-gases seems to be a very attractive one. By mixing these new gases with the traditional natural gas, it becomes possible to have a smooth and economically durable transition. The amount of new gases added may be dependent on the availability, progress of technology and safety and regulatory issues. This is very much like what is already been done with electrical energy sources like wind or solar power. However, unlike electricity, gas comes in a wide variety. Unfortunately appliances and machines currently running on gas are designed to operate only within a very strict window of gas compositions. To be able to widen this band, it is required to have machines that can adapt, depending on the available gas composition. It is therefore required to be able to measure this composition. This thesis describes the first steps in the design and development of an infrared absorption multi-gas micro-spectrometer for the measurement of the concentrations of Carbon Monooxide, Carbon Dioxide and Hydro Carbons in a composite gas. This includes mathematical modeling, design and fabrication. From the model it is found that it should be possible to design a system which is capable of detecting all these gases with sufficient accuracy and over their total dynamic range. Test structures have been designed and partly fabricated, giving great insight in the limitations, restrictions and tolerances of the fabrication process.