CMS poisoning

       Carbon Molecular Sieve (CMS) is the core consumable of PSA nitrogen generators. Once poisoned, it leads to reduced nitrogen output, insufficient gas purity and rising air-to-nitrogen ratio, shortening service life significantly. The five common poisoning causes are water soaking, oil fouling, acid gas corrosion, high-temperature degradation and dust coking. Most operators only spot CMS pulverization while ignoring poisoning as the root cause. This article analyzes symptoms, causes and field solutions for each failure.   Type of Poisoning Symptoms Causes Solution Water Flooding Poisoning Lower N₂ purity & output; CMS caking; higher air-nitrogen ratio Poor air drying; condensed water or moisture backflow Long-time no-load purging; hot air drying; repair pre-drying system Oil Contamination Poisoning Black & sticky CMS; permanent capacity drop; unable for 99.99% high purity Compressor oil leakage; failed pre-oil filtration Light pollution: high-temperature N₂ regenerationHeavy pollution: replace full CMS and filters Acid Gas Corrosion Poisoning Brittle CMS; more powder; higher tower pressure drop; low N₂ recovery Sulfide & acidic gas in raw air erodes carbon structure Replace corroded CMS; add activated carbon pre-filter High-Temperature Degradation Poisoning Fragile CMS; failed high-purity nitrogen production; performance decay Overheated inlet air (>45℃); poor heat dissipation Control inlet temperature at 20–35℃; replace thermally damaged CMS Dust Coking Poisoning High tower pressure difference; blocked pores; reduced gas yield Dust and organic residue coking inside micropores Screen and regenerate CMS; install intake dust filter   In short, proper inlet air pretreatment against water, oil, acid and dust is the key to avoid CMS poisoning and keep long-term stable adsorption efficiency. Effective pre-treatment helps maintain consistent nitrogen purity and rated gas output, greatly extending the service cycle of carbon molecular sieve.