Intrinsically safe PhoCheck Model 5000 employs photo ionization method to find and monitor VOC leaks. Detector responds to nonane, octane, acetone, benzene, formaldehyde, isobutane, and hundreds of other gases and mixtures. It senses leaks as faint as 10 ppb; logs up to 4,000 readings; issues visual/audible alarms; and grants access to all functions with 6 keys. UV lamps change out easily.