... LEL,%VOL Programmable alarm operation value 4-20mA Smart Toxic Gas DetectorTechnical features * 4-20mA, 2 wire connection , ... maintenance. * Multi-parameter backlight LCD display: measuring range,digital gas reading ,units, bar graph , system status etc.* International ... LEL,%VOL* Operating temperature: -40~70°C (According to gas sensor operating conditions)* Humidity: 10-95%RH (non condensing)* ...