The detection of gases via their absorption bands in the mid infrared portion of the spectrum is discussed. Various fibre optic probe designs suitable for use with Fourier Transform Infrared (FTIR) spectrometers are described. The probes fabrication and evaluation with various gases, hydrocarbons and flue gas products are described. Porous clad fibres, tapered fibres, special capillary type fibres and fibre fed transmission cells are all used and their minimum detection concentration (MDC) values quoted for various gases. Evanescent wave absorption spectroscopy of relevance to both the porous clad and tapered fibre probes is compared to the direct transmission cell spectroscopy in terms of sensitivity. The poor sensitivity of the tapered fibre probe is attributed to the underfilled local numerical aperture in the sensing region. The potential of evanescent wave fibre probes coupled to FTIR spectrometers is discussed in the context of both inflammable gas detection and flue gas analysis. Experimental detection limits of various gases are reported and compared to model predictions.