Confined Spaces 27 Appendix B - Additional Resources SDSs for common atmospheric hazards Carbon Monoxide Hydrogen Sulfide Methane Sewer Gases Alternate plan for entry into steam tunnels This alternate plan developed by the Iowa StateUniversity Utilities Department is being included to illustrate how they are addressing the steam distribution tunnel system. Departments with similar situations may be able to use this as a guide to develop alternative procedures for their areas. Alternative procedures must include justification for the plan, entry procedures, emergency procedures, and monitoring and inspection data to support their use. EH&S will assist with the development of alternative procedures as necessary.