natural gas-based channel black

例句：

1. 1. The engineer used a special toolto remove the channel black from the pipeline.
   工程师使用特殊的工具从管道中移除了通道黑。
2. 2. The black channel in thetunnel was causing problems with the ventilation system.
   隧道中的黑色通道导致通风系统出现问题。
3. 3. The black channel was difficult tosee and required extra care when working nearit.
   黑色的通道难以看见，在附近工作时需要额外小心。