Workplace Pulmonary Function Testing

A Health Evaluation System & Information Service - Fact Sheet


The main way workers are exposed to chemicals in the workplace is through breathing substances into their lungs. Some chemicals do little more than cause discomfort and irritation to the nose or throat. Others may cause severe physical damage and lung disease.

Pulmonary (lung) function tests (PFTs) are tools used in the diagnosis of lung disease. Most lung diseases take many years of exposure to develop. Symptoms of lung disease such as shortness of breath, wheezing and coughing usually develop gradually. These tests can often identify problems early in the course of disease, sometimes before physical examinations or chest X-rays. While PFTs by themselves cannot determine the cause of any abnormality, they can be used in combination with other tests to help determine what type of lung disease a person has.

Studies of lung function range from relatively simple tests which can be done at the workplace to complex tests which are done in a medical laboratory. This fact sheet concentrates on spirometry, a type of lung function test which can be done at the workplace and explains how it is done and what it shows.

How Your Lungs Work

The main job of your lungs is to bring oxygen into your body and get rid of carbon dioxide in your blood. When you breathe, the lungs and chest wall act as a bellows to bring in fresh air. The upper airway carries air to the lungs. The lower airways branch out like a tree. The branches end in tiny air sacs called alveoli, where oxygen passes into your blood while waste gases such as carbon dioxide are returned from your blood and breathed out.

The lung's defense mechanisms can become overloaded and worn out by too much exposure to dusts and fumes for too long a time. This can allow lung tissue to be damaged. Healthy lung tissue is elastic; it can expand and contract. Some lung diseases interfere with the lungs' elastic property and make the lungs "stiff." Stiff lungs often cause the lung volume to be reduced, which is called lung restriction. Other diseases can cause airways obstruction, a narrowing of the tubes of the lung. Airways obstruction reduces the rate at which air can pass through the airways. Both lung restriction and airways obstruction can be caused by overexposure to certain chemicals.

When you inhale, you can breathe in particles, dusts, fumes, vapors and other foreign substances. Your body has a natural defense system for ridding itself of these substances.

NOSE: Large particles are trapped in mucus and hair. They are blown out when you blow your nose.

AIR TUBES: Particles which land on the walls of air tubes are caught in mucus. Tiny hair-like fibers (cilia) move the particles up the airways. They are then coughed out or swallowed.

AIR SACS: Dust particles which are tiny enough to reach the air sacs are surrounded by special white blood cells. These cells move particles to where they can be coughed out or swallowed.


Spirometry testing is useful for determining: 1) if a person has lung disease; 2) what type it is; 3) whether a person is getting better or worse; and 4) how impaired a person's health is.

The basic test of mechanical lung function can be done with a spirometer. (A spirometer is an instrument used to measure the volume of air entering and leaving the lungs.) To do the test, a person inhales fully and then blows out the air in his or her lungs through a tube as hard, fast and completely as possible. The test is repeated until at least two of the exhaled breaths are as good as possible. The spirometer measures the amount of air expelled and the speed at which the lungs can be emptied. These measurements are useful in evaluating respiratory disease. These measurements are called FVC and FEV1, and are described below.

Forced Vital Capacity (FVC) is the maximum volume of air that can be blown out at maximum speed after a full breath is taken. AN FVC between 80% and 120% of the predicted level is considered normal. When lungs are stiff because of diseases of the lung tissue, such as pneumonia or lung scarring due to asbestos exposure, they often show reduced lung volume. When a disease causes this type of abnormality, it is called a restrictive lung disease. A normal FVC means itr is unlikely that a person has a restrictive lung disease. The FVC can be low for other reasons, such as chest pain, other types of illness or lack of effort.

Forced Expiratory Volume in One Second (FEV1) is the maximum volume of air that can be exhaled during the first second of a complete, fast, forced expiration. An FEV1 between 80% and 120% of the predicted level is considered normal. FEV1 is useful in diagnosing obstructive lung disease. FEV1 is reduced when the airways (bronchial tubes) are narrowed or obstructed, as in asthma. It can also be reduced in restrictive lung disease.

Ratio of FEV1\FVC - The ratio of the two values is useful in determining the type of lung disease a person may have. A ratio of 0.7 or above is considered normal. The ratio of FEV1 to FVC may be reduced in the presence of airway obstruction, but the ratio is normal in restrictive lung disease.

How Are Tests Interpreted?

An individual's lung function test results are interpreted by comparing them to the results predicted for a person of the same sex, age, height and race.

Rights and Responsibilities

 Employers are required to protect workers from overexposure to hazardous substances.  If overexposures cannot be prevented by engineering or other controls, then personal protective equipment, such as a respirator, is required. In these cases, employers must develop and follow a respiratory protection plan which includes medical evaluation, fit testing, maintenance and training.  In addition, workers exposed to certain health hazards, such as cotton dust or asbestos, must be given periodic PFTs.