This detector uses highly accurate electrochemical sensors to measure concentrations of oxygen. Unit automatically records the last 50 alarm or test events and has active data-logging. This instrument features superior dust and water protection, excellent impact resistance, great RFI performance, and an extremely effective alarm system. Adjustable alarm set points are offered for "low" and "high" levels on all units. A distinct alarm is indicated by two bright flashing LEDs, a piercing audible alarm, a flashing notification on the LCD, and an internal vibrating alarm, helping to ensure that no alarm condition will go by unnoticed.