Vim li cas tunnels siv tawg-pov thawj teeb

Kev tawg ntawm cov pa hluav taws xob, xws li methane, feem ntau tshwm sim hauv tunnels. Kev tswj hwm kev nyab xeeb kev tsim kho yuav tsum tau siv cov khoom tawg-pov thawj teeb pom kev zoo.