The idea that blank cartridges are harmless is one of the most harmful fraudulent tropes that Hollywood and filmmakers have perpetuated.
No they are not as dangerous as bullets,but being shop with one can still kill.
For example,
https://en.wikipedia.org/wiki/Jennifer_O%27Neill Jon-Erik Hexum, O'Neill's co-star in the Cover Up television series, mortally wounded himself on the show's set, unaware that a gun loaded with a blank cartridge could still cause extreme damage from the effect of expanding powder gases. He died six days later.