Buying or selling Air Liquide shares can be done through an online broker or an online bank that offers a trading service. It is important to choose a trusted broker that offers a reliable and secure trading platform. Air Liquide shares are listed on the Euronext Paris market, so it is possible to buy or sell them via an online trading platform specialising in this market. Investors can also buy or sell Air Liquide shares via CFDs (contracts for difference) offered by some brokers. It is important to bear in mind that buying shares involves risk and investors should be aware of these risks before making an investment decision. It is recommended to follow company news, monitor financial performance and consult market analysis before making a decision to buy or sell Air Liquide shares.