Carbon nanostructures with zigzag edges exhibit unique properties with exciting potential applications. However, we show here that such nanostructures are often unstable under ambient conditions even if they display a predominantly closed-shell character. In fact, exemplified with narrow chiral graphene nanoribbons (chGNRs), we show how low pressures of pure oxygen gas readily oxidize the ribbons in spite of their predominantly closed-shell character. The oxidation has dramatically disruptive effects on their electronic properties, which severely jeopardizes their potential applicability. That is, the lack of stability is a barrier that must be surmounted to allow for a scalable exploitation of this type of materials. We prove the viability of chemical protection/deprotection strategies for this aim on the same chGNRs. Upon hydrogenation, the chGNRs survive an exposure to air, after which they are easily converted back to their original structure via annealing. We also approach the problem from another angle. Determination of the most reactive sites and of the nature of the main oxidation products allowed us synthesizing a chemically stable oxidized form of the chGNRs that can be subsequently converted to the pristine hydrocarbon form via hydrogenation and annealing. These findings can be extrapolated also to other carbon nanostructures with zigzag edges and may open new doors toward their integration in devices.