On our team we consider hazmat technician to be the bare minimum requirements...a starting point if you will, so haz-mat ops...is "enough to be dangerous/defensive". We assume after that level you'll know enough to be defensive minded, recognize the hazard(s), clear the area and wait for help.
Our department requires everyone department wide to be trained to the Operations level. That way we don't need to use what few techs we have to set up a decon line. A tech can oversee it as Decon officer, but we can use operations level personnel to man the line.