Spirometry is a simple test that can help diagnose and monitor certain lung conditions. It can be used as part of ongoing health surveillance and fitness-to-work assessments, particularly for employees who wear respirators or are exposed to particular chemicals, dust, fumes, asbestos and lead.

It is carried out using a spirometer, which is a small machine attached to a mouthpiece. The employee will breathe in and then exhale into the mouthpiece. The spirometer measures:

• Forced expiratory volume in one second (FEV1). This is the amount of air you can blow out within one second.
• Forced vital capacity (FVC). The total amount of air that you blow out in one breath.
• FEV1 divided by FVC (FEV1/FVC). Of the total amount of air that you can blow out in one breath, this is the proportion that you can blow out in one second.

The test will often be repeated at least three times to ensure a reliable result. Height and weight will be measured before the test and the results of the test will be compared to ‘normal’ readings of someone of the same gender, age, height and weight.

The test can be used to look for any signs of new or worsening occupational-related diseases, including occupational asthma.

Find out about other diagnostic tests for the workplace.