4. Linear approach using cross-linked graphs ranked by accessibility to the contaminating agent

This approach corresponds to the reality of the materials under consideration. The porous medium behaves like a network of interconnected pores, some of which are accessible (open) to the contaminant and others inaccessible or "closed" (isolated clusters on the graph).

Inaccessibility may depend on other parameters such as –– the contagion power or fluidity of the percolating product.

The notion of accessibility to the contaminating agent is therefore relative, and may depend on the characteristics of the environment, its complexity and its interaction with the contagious agent.

These variations can simply be observed in real-life situations, and can then be used to approach critical situations.

The skeleton of the network or graph representing the environment (or population) can be broken...