How does THCA convert to THC when vaping?

When you heat an indica THCA vape, the process of decarboxylation converts THCA into Delta-9 THC -the compound responsible for psychoactive effects. This conversion happens almost instantly at vaping temperatures, which is why THCA vapes produce effects similar to traditional THC products. This is also why THCA is federally legal in raw form but behaves like THC when consumed.