Laboratory scale flow reactors are ideal systems for using gases, particularly those that are toxic or associated with other hazards.  The gas reactions that have been most successfully adapted to flow are hydrogenation and carbonylation,  although work has also been performed using other gases, e.g. ethylene and ozone.
Reasons for the suitability of flow systems for hazardous gas handling are:
*Systems allow the use of a fixed bed catalyst. Combined with low solution concentrations, this allows all compounds to be adsorbed to the catalyst in the presence of gas
*Comparatively small amounts of gas are continually exhausted by the system, eliminating the need for many of the special precautions normally required for handling toxic and/or flammable gases
*The addition of pressure means that a far greater proportion of the gas will be in solution during the reaction than is the case conventionally
*The greatly enhanced mixing of the solid, liquid, and gaseous phases allows the researcher to exploit the kinetic benefits of elevated temperatures without being concerned about the gas being displaced from the solution