We can supply GD518 series is to detect natural gas or propane gas. GD518L: liquefied propane gas detector with DC output GD518N: natural gas detector with DC output GD518LR: liquefied propane gas detector with Relay output GD518NR: natural gas detector with Relay output Features: 1) 4 wire models 2) FIGARO semiconductor sensor heads used for gas detection 3) Loud 70 dB sound signal at alarm mode 4) Advanced detection and discrimination algorithms 5) Easy installation and maintenance 6) Durable sensor head, no need for replacement 7) SMD circuit board design- quality and reliability guaranteed 8) Magnet test feature 9) Five-year limited warranty