Min. life span of the molecular sieve is 5~8 years for ZMS (zeolite molecular sieve for oxygen production) and  6~10 years for CMS (carbon molecular sieve for nitrogen production) under standard working conditions and scheduled maintenance for all parts. The feeding air quality is most important for the performance of molecular sieves. With good maintenance, one of CAN GAS PSA Plant in Bangladesh has been running well for over 13 years without any replacement of molecular sieves.