Although molecular sieves are crucial to the well-being of a modern gas plant, they aren’t always given appropriate attention due to their relatively minor cost compared to the overall cost of the plant. Unless careful consideration is given to the design conditions for the dehydration unit, it is easy to underestimate the severity under which the molecular sieves are expected to perform. Proper understanding of sieve capabilities, operating requirements and above all their limitations can greatly simplify plant operations and will have a significant impact on future plant operating and maintenance costs.