Internal pump continuously pulls gas samples from flue or ambient air more quickly and steadily than "non-pump" or "absorption" type analyzers. Unique pump standby switch extends battery life and speeds walk-through testing. Flue probe and flexible hose connect easily and securely. Switchable backlight for viewing in dark environments. Thumb-wheel added for easier zero adjust control. New case design fits in your hand with the power and backlight switches at your fingertips. Electrochemical sensor will last for two years