This construction safety toolbox talk explains common confined-space hazards, such as manholes, crawl spaces, and tunnels. It includes a real incident involving methane gas exposure, steps workers should take to stay safe, and reminders about training, communication, monitoring, and emergency planning. The back side of the talk includes an illustration of the hazard and solution, plus reminders of key steps to avoid injury or illness.
https://www.cdc.gov/niosh/publications/numbered/2026-109.html