Pulmonary function testing is a valid approach to comparing the lung volume, capacity, and gas exchange, against the baseline focused on the general health of the lungs. Spirometry and plethysmography are two PFT variations that technicians use to assess lung tissue function and health. The former involves a mouthpiece sealed around the patient's mouth while, conversely, the latter consists of a patient sitting inside an airtight compartment.

The PFT procedure combines the average value of select measurements giving insight into whether the test subject has a pair of healthy lungs. Tidal volume (VT), or the amount of air expelled from the lungs during normal breathing, forced vital capacity (FVC), a quick, forceful expulsion of air after inhaling, and total lung capacity, the cumulative amount of air held in the lungs are a few examples. A PFT technician notes and compares their findings that either dismiss or indicate chronic lung problems exist.

A healthcare provider may recommend PFT testing to see to what degree breath intake and expulsion fluctuate, which may require follow-ups to show the difference over time. This method can serve in the workplace, where repeated exposure to airborne pollutants calls for PFT testing to help classify if employees are fit to work.