Written and maintained by CASRAI Editorial Board
Last updated
This page describes products and general use; it is not medical advice.
A spirometer mouthpiece is the single-patient part a person breathes through during a spirometry test, and in current practice it usually comes as part of a disposable in-line filter. Clinic staff, buyers and students searching for it generally need to know what the part does, what the ATS/ERS standard says about it, and how it fits into daily calibration checks.
What a spirometer mouthpiece is
A diagnostic spirometer is, in the words of the US federal regulation, a device used in pulmonary function testing to measure the volume of gas moving in or out of a patient’s lungs; it is regulated as Class II (21 CFR 868.1840). The mouthpiece is the part between the patient and that device. The 2019 ATS/ERS spirometry standard says the use of disposable in-line filters has become standard practice in most facilities and that the mouthpiece is usually an integral part of the filter, which reduces contamination of the spirometer.
Who uses it: technicians and nurses who run spirometry in clinics, occupational health and hospital lung-function labs, and the staff who stock those rooms.
Mouthpiece versus in-line filter
The two terms often describe one product. Because the standard describes the mouthpiece as usually built into the filter, a listing for a “bacterial/viral filter” and one for a “mouthpiece” may be the same item for a given spirometer; the instructions for use of your device say which parts it accepts.
Types and variants
| Item | What the ATS/ERS 2019 standard says |
|---|---|
| Disposable in-line filter with integral mouthpiece | Standard practice in most facilities; reduces contamination of the spirometer. Disposed of at the end of the testing session along with other disposable items. |
| Reusable spirometer parts | Manufacturers must describe acceptable cleaning and disinfecting methods, including recommended chemicals and concentrations. |
Shape (round, oval, flared) is not settled by the standard, so product choice beyond the table above comes from the device manufacturer’s instructions for use.
Calibration and the mouthpiece
This is the connection most product listings leave out. The ATS/ERS standard states that if an in-line filter is used in spirometry testing, it must also be used during recalibrations and verifications. The reason is that the filter is part of the airflow path being checked.
How often is spirometer calibration verified?
Calibration verification must be done at least daily, using a 3-L syringe cycled at least three times to give a range of flows (the standard specifies 0.5 to 12 L/s). Verification is the check that the device is within limits.
What accuracy is required?
| Item | Requirement (ATS/ERS 2019) |
|---|---|
| Calibration verification limit | ±3% (±2.5% for the spirometer plus ±0.5% for the calibration syringe), for inspiration and expiration at each flow |
| 3-L calibration syringe | Accuracy of ±0.015 L or ±0.5% of full scale; the manufacturer must recommend intervals between syringe accuracy checks |
| Verification frequency | At least daily, syringe cycled at least three times |
Safe use and handling basics
- The operator washes hands or uses an approved hand sanitizer before contact with each new patient.
- Filters, mouthpieces, noseclips and gloves are single-session items and are disposed of at the end of the testing session.
- Follow the manufacturer’s cleaning and disinfection instructions for any reusable parts, and any additional local infection-control policy.
Common mistakes
- Verifying calibration without the filter that is used on patients; the standard requires the same filter during recalibration and verification.
- Treating a mouthpiece and a filter as separate purchases without checking whether the filter already includes the mouthpiece.
Related pages
For a different device, see what an incentive spirometer is and what a peak flow meter is. Consumables for a testing room are listed in the occupational medicine clinic supply checklist. Suppliers list items in the diagnostic, monitoring and imaging category.
FAQ
Is a spirometer mouthpiece the same as a filter?
Often yes. The ATS/ERS 2019 standard says the mouthpiece is usually an integral part of the disposable in-line filter.
How is spirometer calibration checked?
Calibration is verified at least daily with a 3-L syringe cycled at least three times, using the same in-line filter as for patients; the result must be within ±3%.
When is a mouthpiece thrown away?
Disposable filters and mouthpieces are disposed of at the end of the testing session.
Sources
- Graham BL et al. Standardization of Spirometry 2019 Update, an Official ATS/ERS Technical Statement. Am J Respir Crit Care Med 2019;200(8):e70-e88. https://pmc.ncbi.nlm.nih.gov/articles/PMC6794117/ (checked 2026-10-30).
- 21 CFR 868.1840, Diagnostic spirometer. https://www.law.cornell.edu/cfr/text/21/868.1840 (checked 2026-10-30).
