The Altair Pro detector uses highly accurate electrochemical sensors to measure concentrations of toxic gas (ammonia, carbon monoxide, chlorine, hydrogen cyanide, hydrogen sulfide, nitrogen dioxide, phosphine and sulfur dioxide) or percent oxygen depending on instrument version. This measurement is clearly displayed on the instrument's LCD. The detector is fast-responding and has clear alarm functions to alert the wearer. The Altair Pro detector automatically records the last 50 alarm or test events and has active data-logging. To read data or change alarm set points simply connect the unit to an MSA infrared adapter using the built-in IR communication port. These detectors accurately measure the gas concentration or percent oxygen (depending on model) and display this information on a large, clear, backlit LCD. The ALTAIR Pro single-gas detector 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. In addition, the toxic gas versions also have TWA and STEL alarm points. 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. With current sensor options for CO, H2S or O2, the Altair Pro single-gas detector will provide worry-free performance and stand up to the roughest handling in even the toughest industrial environments. The sensors and battery can easily be replaced to keep the unit performing perfectly for years. Its rubberized armor housing and one-button operation provide the durability and simplicity you expect.