Can you do RT tasks without a license?

Your humble question:  Do you have to have a license to do RT tasks?

While some states don't require a license, most now do.  However, you do not have to have a license to do some RT tasks.  You can do breathing treatments, EKGs, PFT, EEGs, and basic RT therapy without a license.  However, you must meet competency requirements by the institution and you must work under the license of a licensed respiratory therapist.  In essence you will be working under that person's license, and he will be responsible for the work you do.