solvent exhaust

Solvent exhaust systems in semiconductor fabs extract and treat vapors from organic solvents and volatile organic compounds (VOCs) used in photoresist coating, developing, stripping, and wafer cleaning processes. Common solvents include: PGMEA (propylene glycol methyl ether acetate — primary photoresist solvent), PGME (propylene glycol methyl ether), NMP (N-methyl-2-pyrrolidone — resist stripper), IPA (isopropyl alcohol — drying agent), acetone, EL (ethyl lactate), and DMSO (dimethyl sulfoxide). These solvents are flammable, and their vapors pose both health and fire/explosion hazards, requiring specialized exhaust design distinct from acid, toxic, and general exhaust systems. Key design requirements include: explosion-proof construction (all electrical components in the exhaust path — fans, dampers, sensors — rated for Class I Division 1 or 2 hazardous locations per NEC/NFPA), LEL monitoring (Lower Explosive Limit sensors continuously monitoring solvent vapor concentrations — typically alarming at 25% LEL and shutting down at 50% LEL to prevent explosive concentrations), fire suppression (clean agent or CO₂ suppression systems in ductwork and plenums), static dissipation (conductive or static-dissipative duct materials and grounding to prevent static discharge ignition), adequate velocity (maintaining minimum transport velocity of 2000-3500 fpm to prevent vapor accumulation and condensation in ductwork), temperature control (preventing condensation that could create liquid solvent accumulation — heated ductwork sections where needed), and VOC abatement (thermal oxidizers, catalytic oxidizers, regenerative thermal oxidizers, or activated carbon adsorption to meet air quality emission permits — many jurisdictions require 95-99% destruction efficiency for VOC emissions). Solvent exhaust is always kept completely separate from acid and toxic exhaust systems to prevent dangerous chemical reactions between organic solvents and oxidizing acids. The ductwork material for solvent exhaust is typically stainless steel (not FRP, which is used for acid exhaust, because solvents can attack certain resins).