Written and maintained by CASRAI Editorial Board
Last updated
General product information only, not medical advice. Choosing and using an airway for a patient is a clinical decision made by trained staff following the manufacturer’s instructions for use and local protocols.
An oral (oropharyngeal) airway is sold in a graded series of sizes, and the size is identified three ways: a length in millimetres, an ISO size number equal to the length in centimetres, and a colour on the flange. The chart below shows the full series from one named specification, then explains how ISO numbering relates to the length.
Oral airway size chart (Guedel type, single-use)
Source: the Médecins Sans Frontières (MSF) Unicat catalogue specification for single-use Guedel oropharyngeal airways, which cites ISO 5364:2016 (Anaesthetic and respiratory equipment – Oropharyngeal airways) and checked on 2026-10-30. The "Use" column is MSF’s own label.
| ISO size | Length (mm) | Internal diameter | Flange colour | Use (MSF label) |
|---|---|---|---|---|
| 4 | 40 ± 2.5 | 3.0 mm | Pink | Neonate |
| 5 | 50 ± 2.5 | 3.5 mm | Blue | Baby |
| 6 | 60 ± 2.5 | 4.0 mm | Black | Small child |
| 7 | 70 +5.0 / -2.5 | 4.0 mm | White | Child |
| 8 | 80 ± 5.0 | 4.5 mm | Green | Adolescent |
| 9 | 90 ± 5.0 | 4.5 mm | Yellow | Adult |
| 10 | 100 ± 5.0 | 5.0 mm | Red | Large adult |
Check your product’s labelling. The flange of the airway in your hand, and the manufacturer’s instructions for use, are the authority for that product. This chart describes one catalogue specification and is not a substitute for them.
How to read the chart
The MSF specification states that the size is identified on the flange of the airway, that the ISO size equals the length in centimetres, and that the flange carries the colour defined by the standard. So size 9 means about 90 mm, and the 90 mm airway has a yellow flange. The length column carries a tolerance: ± 2.5 mm for the 40 to 60 mm sizes, +5.0 / -2.5 mm for the 70 mm size and ± 5.0 mm for 80 mm and above. A measured airway can therefore differ slightly from its nominal length without being out of specification.
Numbering and ordering notes
Length in millimetres is the one value that does not change between numbering schemes, which is why it is the safest value to quote when ordering, stocking or documenting. Some listings add their own brand "Size" selector next to the ISO number: a Cardinal Health Guedel airway listed by McKesson is described as "Yellow 90 mm Length ISO 9 NonSterile Adult" and also offers a separate Size selector (checked 2026-10-30). Because a bare "size 4" can mean different things in different catalogues, state the ISO number together with the length in millimetres.
Equivalence notes
- ISO number to millimetres: multiply by 10 (size 9 = 90 mm), per the MSF specification.
- Colour to size: MSF describes its flange colour as the one defined by the ISO standard. The flange number or length is still the value to confirm.
- Sterile or non-sterile: sold as either. MSF lists sterile and non-sterile versions, and the Cardinal Health listing above is non-sterile.
Common mix-ups
- Reading the colour instead of the label. Colour is a visual cue printed alongside the size, not a replacement for it.
- Mixing numbering schemes. In ISO numbering, size 4 means 40 mm; a brand’s own Size selector may use different numbers, so quote the length too.
- Confusing oral and nasal airways. An oropharyngeal airway goes through the mouth; the FDA regulation (21 CFR 868.5110) describes it as "a device inserted into a patient’s pharynx through the mouth to provide a patent airway". Nasal airways are a different device with their own sizing.
- Assuming an airway is reusable. The MSF specification describes the devices above as single-use.
Regulatory status
The U.S. Food and Drug Administration classifies the oropharyngeal airway as Class I under 21 CFR 868.5110, exempt from premarket notification (510(k)) subject to the limitations in 21 CFR 868.9 (checked 2026-10-30).
Where airways sit in related equipment lists
Oral airways appear in emergency-equipment lists such as the emergency response cart checklist for outpatient clinics, the EMS jump bag restocking checklist and the crash cart overview. For other airway devices see laryngeal mask airway sizes, the endotracheal tube guide and the bag-valve-mask guide.
FAQ
What size is an adult oral airway?
In the MSF/ISO-based specification above, adult is size 9 (90 mm, yellow) and large adult is size 10 (100 mm, red). Cardinal Health’s listing also labels its 90 mm ISO 9 airway "Adult". Confirm against the product label and instructions for use.
Does the ISO size number equal the length?
Yes, in centimetres, per the MSF specification: size 9 is 90 mm.
Are oral airway colours standardised?
The MSF specification describes the flange colour as the standard colour defined by ISO. Because some makers also print their own brand size numbers, rely on the flange label and the manufacturer’s documentation rather than colour alone.
Are oral airways sterile?
They are supplied both ways. The MSF catalogue lists sterile and non-sterile single-use versions.
Sources
- MSF Unicat, "Oropharyngeal airway, s.u." product specifications (non-sterile 50 mm, product 84069; sterile 80 mm, product 83356), citing ISO 5364:2016 and ISO 18190:2025, checked 2026-10-30: unicat.msf.org/cat/product/84069
- Cardinal Health Guedel Oropharyngeal Airway, McKesson listing 741312, checked 2026-10-30: mms.mckesson.com/product/741312
- 21 CFR 868.5110 Oropharyngeal airway, checked 2026-10-30: law.cornell.edu/cfr/text/21/868.5110
