posted in: Technical Insights


A spirometer is a tool used by medical professionals to diagnose different types of lung conditions and for initial lung functionality tests. It can be used in monitoring the recovery of a patient who have had surgery and is experiencing weakness when taking deep breaths. Common illness associated with the use of a spirometer testing include asthma, COPD (chronic obstructive pulmonary disease), and pneumonia.

How it works

This is a non-invasive pulmonary function test, meaning that all test parameters are measured from outside the body. The test measures the patient’s lung air capacity, volume, rate of gas exchange and flow speed. The patient will either blow or inhale into the mouth piece of a spirometer module. The spirometer will then measure speed and volume of a breath inhaled or exhaled from the lungs during a period of time. From here a RT (Respiratory Therapist) or other health care professional can determine if the patient is suffering from COPD or asthma, which are the most common types of breathing problems diagnosed with this device.

Preventive Maintenance (PM)

All annual preventative maintenance tests start with a thorough electrical safety test. Inspections of all power supplies, power cords, cord caps and cases. Preventative maintenance of a spirometer includes internal cleaning, disinfecting, inspection of external surfaces, hoses, adapters and seals. Also, during the annual PM, manual calibration is also performed using a calibrated 3L syringe. The spirometer will be calibrated to the manufactures specifications typically within ±3.5 percent of accuracy. Calibrating insures that there are no leaks in the system.

Common failures

Shown below is a brief list of the common failures that we see on spirometers during our routine preventative maintenance checks.

  • An electrical safety concern: An electrical safety concern means that something we were testing electrically on the unit was noted to be unsafe, and this could include damaged cables, exposed wiring, and failed leakage current test.
  • Physical Inspection: During our preventative maintenance check one of the first things that we test or inspect is the case of the unit. Here we compete an exterior inspection of unit, which we look for signs of drops or user damage, and we check all of the interface cable connection pins for damage.   During this inspection, we can see a damaged case / housing of the spirometer or damage to one of the interface cables which we would note in our documentation.  Lastly, we check all of the accessories to make sure they have not been compromised which typically will show up as a crack or small hole in the accessories which causes an air leak.
  • Calibration Failure: We will typically attempt to calibrated the unit up to three times, and after that we will note that the unit had a calibration failure. This failure could be attributed to several conditions and the most common are pushing the 3L syringe plunger too fast or too slow during calibration, leaks, faulty transducers, and internal malfunctions.  Before marking the unit as failed we will try our best to remove any obstructions in the air ways as this could cause a failure as well.
  • Failed leak test: A failed leak test could be a reason why the unit failed the calibration noted above.  Leaks can typically be found around the hand piece transducer where the technician connects the disposable mouth pieces, and damaged tubing will cause failed test results.
  • Internal malfunctions: An internal malfunction on the unit typically means that a sensor of main board has failed inside the unit. For this failure, we will need to consult service manuals for any error codes that may occur during testing or calibrations.

TRH Services Value

By choosing to use TRH Services to test and maintain your spirometers you can rest assured that we are equipped to handle the maintenance on these units and the repairs.  We will be able to calibrate your spirometers to a high standard and provide you with a certification report that you can provide your study or accreditation board. By completing maintenance on a regular basis on your spirometer it will help extend it’s useful life as we will help keep it within the manufacturer’s recommend specifications. We complete our onsite service of these devices across South-Western Ontario (London, Toronto, Kitchener, Waterloo, Cambridge, Guelph, Hamilton, etc.).


 Common Spirometers

Listed below is a brief list of spirometers that we work on a regular basis:

ManufacturerModel Number
CareFusion CorpMicro Loop
CareFusion Corp3.0L Syringe
Hans Rudolph Inc.3L Calibration Syringe (5530)
KoKoMateKoko USB
Medical International Research (MIR)Spirolab III Colour
Welch AllynSpiroPerfect
Welch AllynSPIRO-S
Welch AllynSpirovit SP-2


Written By: Rolando Valladares
Edited By: Tyler Hasenpflug CET