A laser apparatus comprises a laser having a lasing chamber an inlet to the lasing chamber for a lasing gas containing a heavy noble gas and an outlet from the lasing chamber for the discharge of a flow of lasing gas, wherein the outlet is able to be paced in communication with the atmospheric through an adsorptive trap containing a selective adsorbent of the heavy noble gas.In operation, the heavy noble gas (xenon or krypton) is adsorbed in the trap. The trap may be taken to a remote site for the recovery of the heavy noble gas when it is approaching saturation.