What is a significant downside of using an air chisel when removing a door skin?

Using an air chisel for removing a door skin presents risks, notably the potential for damaging the door skin hem flange. The hem flange is a critical structural element that helps maintain the integrity of the door. When an air chisel is used, the power and speed can lead to excessive force, which may inadvertently deform or fracture this important part of the door. It requires a precise and careful technique to avoid such damage, as any compromise to the hem flange could affect the door's ability to fit or seal properly after reassembly or repair.

In contrast, while operation noise is a factor, it is not the most significant concern compared to the risk of structural damage. Similarly, although the process might be slower with other tools, the focus in this context is more on preserving the door’s integrity than on the speed of removal. Lastly, while safety equipment is always important when using power tools, it is a general safety consideration and does not specifically address the unique challenges posed by using an air chisel in this particular task. Thus, the potential for damaging the hem flange is indeed the most noteworthy downside when employing an air chisel for this operation.