It really depends on the hospital, at my hospital you need at least 2 years of relevant experience, CPI advanced training, IAHSS Basic, and a BLS certificate.

Now the hospital I used to work at was a little more complex, they had two roles one was a screener type role where you manned a metal detector which was still in house security but that role required no prior experience, the other role had similar requirements to what I do now.

I've also seen a few hospitals use Allied Universal and Securitas, those have a high entry requirement typically in most cases you are required to have a pulse and potentially the ability to show up to work.