Where another reticulated service, such as air, gas or steam, is connected to primary containment equipment for large scale work (a closed system or LWTS, for example) and could form a cross-connection leading to a GMO being released beyond the certified facility, the need for backflow prevention must be decided by a risk assessment. The guideline suggests that a filter with a pore size of 0.2 µm or less generally suits air and gas, and that suitable filters or other mechanisms that stop backflow should be considered for steam lines.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.