In some cases, the balancing of a reaction using DFS(∆, R, ∅) yields a formally correct solution that is chemically implausible. More precisely, S may contain one or more molecules that are at least unlikely to be the true reactants or products. In some cases, it is possible to find a more plausible rebalancing. Oxygen and halogens are typically formed via potent oxidizing agents. Hydrogen, on the other hand, is usually produced in reactions with alkali metals (e.g., lithium, sodium, potassium) or hydride compounds. Whether this is the case can be checked after DFS(∆, R, ∅) has successfully balanced the reaction. Currently, SynRBL considers only three postprocessing rules: