It has been stated that the weapons used by the humans on Babylon 5, PPGs, are designed to cause harm to living things, but not cause damage to bulkheads, something that would be highly desirable on a space station. When Garibaldi is being chased by bad guys they escape into a ventilation shaft, but the bad guys shoot at them with PPGs. The energy pellets have no problem penetrating into the shaft, nearly hitting Garibaldi and the people he is protecting. This should not be possible... BUT this is not hull-metal.
The air duct is thin sheet metal, anything hull-quality would be considerably thicker. Heck, an common air-rifle can puncture current air ducting.