Given a graph $G$, a coloring $c:V(G)\longrightarrow \{1,\ldots,k\}$ such that $c(u)=c(v)=i$ implies that vertices $u$ and $v$ are at distance greater than $i$, is called a packing coloring of $G$. The minimum number of colors in a packing coloring of $G$ is called the packing chromatic number of $G$, and is denoted by $χ_ρ(G)$. In this paper, we propose the study of $χ_ρ$-critical graphs, which are the graphs $G$ such that for any proper subgraph $H$ of $G$, $χ_ρ(H)

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