The use of reactive gases for syntheses on small laboratory scale is often avoided due to safety concerns so that expensive alternatives are required. The recent development of gas-permeable membrane-based reactors offers new options for safe handling of these gases in a continuous-flow system. A prototype of a gas/liquid system was built to introduce gas in the microreactor. An integrated gas flow controller and inline FTIR analysis were used to safely handle the gas. With the system, the carboxylation of a Grignard reagent with carbon dioxide was chosen as a nonhazardous model reaction to validate the prototype reactor.