45 Minutes. It takes approximately 45 minutes to complete full pulmonary function tests. The first part of the test will involve measurement of your spirometry (fev1 and fvc); you will be required to take large breaths of air and blow them out through a small tube attached to a machine. Next you will measure lung volumes and tlco (see my answer on tlco elsewhere in this section). The test is non invasive.
Blow. You have to blow into a mouthpiece following the instructions that the respiratory therapist will give you. Do not worry but give it your best effort.