Volume of air to solvent must not fall below certain limit. Lower Explosive Limit is concentration of flammable vapors below which they are too lean to ignite. Air recirculation filters must be cleaned weekly. Supply air must not deflect the web, for tension changes would vary the nip to nip distance. On presses running foils, films- rollers support the web at each nozzle.
Steam heat is slow and steady.
Electric heat similar characteristics to steam heat- higher energy cost. Heating coil temperatures can ignite airborne dust or solvents. Need fresh air for combustion. All mentioned methods use air as the heat transfer medium and for the mass transfer of vapors outside the dryer. Air most versatile heat transfer medium and for the mass transfer of vapors outside the dryer.