The MSA Altair for H2s is a reliable high-performance single-gas detector that provides two years or 1080 alarm minutes of service life under warranty with no maintenance. This instrument will not deactivate after two years of operation, but will continue to perform as long as battery capacity allows. No calibration, sensor change or battery change is needed. Altair and can be worn securely anywhere. This rugged clip design keeps the unit attached during event he roughest use.