Patented electrochemical sensors and MSA-built button sensors. Stainless steel and solid electrolyte construction virtually eliminate sensor leakage. Automatically records the last 25 alarm/test events and can communicate data by connecting to MSA Link via built-in IR communication port. No-miss triple alarm system includes bright flashing LEDs, piercing audible alarm and an internal vibrating alarm. Rubberized armor housing and one-button operation for maximum durability and simplicity.