designed carefully and practicality ,visual and audible alarm ,easy to install The ZX-212 flammable gas examination ... 75dB/mpreparation electricity working time >2 hoursconcentration of alarm 25%LEL 50%LELconcentration of alarm error < ±3%LELalarm method sound and light ... : real-time check of data,fault detecting,power management,alarm display,alarm indication ,relay outputs etc ,1 signal for RS-485 ...