Pac Series allows users to select among 18 sensors models for the detection of up to 33 gases. The monitors can detect standard gases such as carbon monoxide, hydrogen sulfide, sulfur dioxide and oxygen as well as special gases such as ozone, phosgene and nitrogen dioxide. Some models are offered with dual sensors for hydrogen sulfide/carbon monoxide or oxygen/carbon monoxide, or a hydrogen-compensated carbon monoxide sensor, to reduce the influence of hydrogen on the indication of carbon monoxide. Alarms are issued acoustically, visually and with a clearly noticeable vibration, and users can access acknowledged alarms at a later time.