Hi Bree, and thanks for posting - you've posed an excellent question!
I see my colleague, , has already made a comment and I do hope you have an opportunity to read what he's written.
I, too, have something to add.
Generally speaking, a proper pulmonary function test can be provided in a doctor's office (who has the proper equipment), or, in a separate pulmonary function laboratory, which is set up for the express purpose of giving the test. A laboratory is usually connected with a physician who specializes in pulmonary medicine. The test is usually given by a (specially trained) respiratory therapist with a prescription for the diagnostic study from the doctor.
I do hope this brief answer provides you with helpful information for your concern.
All the best,
Leon (site moderator COPD.net)