MeasuringRange 2 to 5 ppm 5 to 120 ppm 120 to 312 ppm Number of PumpStrokes 4 2 1 CorrectionFactor 0.4 1 2.6 Sampling Time 2 minutes per pumpstroke Detecting Limit 0.5 ppm (n=4) Color Change White → Darkgreen Reaction Principle C6H6 + I2O5 + H2S2O7 → I2 Coefficient ofVariation 20% (for5 to 40 ppm), 15% (for 40 to 120 ppm) ShelfLife 3Years Correctionsfor temperature & humidity Unnecessary Store the tubes at cool and darkplace.
Possible coexisting substances and theirinterferences (NOTE)
Substance Concentration Interference Change color by itself Hexane 100 ppm No effect No discoloration Toluene 200 ppm No effect No discoloration Xylene 300 ppm No effect No discoloration Aromatichydrocarbons other than benzene are trapped in the brown layer inthe pretreatment tube.If the pretreatment reagent is entirelyconsumed (whole brown layer turns to dark brown),ahigher reading will be given.
Calibration gasgeneration Diffusion tubemethod
TLV-TWA TLV-STEL Explosive range 0.5ppm 2.5ppm 1.3 to 7.1%