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A Venturi mask is an oxygen face mask that mixes a fixed amount of room air into the oxygen supply, so it delivers a set oxygen concentration (24%, 28%, 31%, 35%, 40% or 60%) largely regardless of the oxygen flow rate. This page is for clinic staff, buyers and students who need to know what the device is, how its numbers work and how it differs from other oxygen masks.
This page describes products and general use; it is not medical advice.
What a Venturi mask is
A Venturi mask is a low-concentration, fixed-performance oxygen mask. The US regulation that defines it, 21 CFR 868.5600, reads: “A venturi mask is a device containing an air-oxygen mixing mechanism that dilutes 100 percent oxygen to a predetermined concentration and delivers the mixed gases to a patient.” Its purpose is to give a known oxygen concentration, which is why the British Thoracic Society (BTS) guideline describes it as suitable for all patients needing a known concentration of oxygen.
Who uses it: clinicians in hospitals and emergency settings who prescribe or deliver controlled oxygen, and the supply and clinic staff who stock the masks and their colour-coded adaptors.
How air entrainment fixes the concentration
Oxygen enters the mask through a Venturi adaptor. Air is drawn in through openings (a “cage”) on that adaptor and dilutes the oxygen. The BTS guideline explains that the higher the oxygen flow, the more air is sucked in, so the proportions stay the same and the delivered concentration does not change as flow rises. The guideline states that a Venturi mask gives an accurate concentration of oxygen regardless of the oxygen flow rate, and that the minimum suggested flow rate is written on each Venturi device.
A worked example from the BTS guideline (Figure 11 caption): a 24% mask run at about 2 L/min of oxygen produces a total gas flow of about 51 L/min, and a 28% mask run at about 4 L/min produces about 44 L/min. The lower the concentration, the more air is entrained per litre of oxygen. The guideline notes that this total flow often exceeds the patient’s own inspiratory flow rate.
Concentrations available
| Concentration | What the BTS guideline says |
|---|---|
| 24% | Available; 24% and 28% masks are particularly suited to those at risk of carbon dioxide retention. Figure 11 example: about 2 L/min oxygen gives about 51 L/min total flow. |
| 28% | Available; particularly suited to those at risk of carbon dioxide retention. Figure 11 example: about 4 L/min oxygen gives about 44 L/min total flow. |
| 31% | Available. |
| 35% | Available. |
| 40% | Available. |
| 60% | Available. |
Source: BTS Guideline for oxygen use in adults in healthcare and emergency settings (Thorax 2017;72:i1-i90), section 10.2.3 and Figure 11. Who should receive which concentration, and the target oxygen saturation range, are clinical decisions covered by that guideline and by the treating clinician, not by this page.
Venturi mask compared with other oxygen devices
| Device | Delivered oxygen, per BTS | Key difference |
|---|---|---|
| Venturi mask | Fixed 24-60% depending on adaptor | Concentration is set by the adaptor, not by raising the flow rate. |
| Simple face mask | 40-60% | Should not be used below 5 L/min (about 40%). |
| Nasal cannulae | Inspired oxygen cannot be predicted | Concentration varies with the patient and the flow. |
Related reading on CASRAI: non-rebreather masks, nasal cannula flow rates and sizing, CPAP and oxygen mask types and aerosol masks.
How to choose: what the guideline says
The BTS guideline describes Venturi masks as suitable when a known oxygen concentration is needed, with 24% and 28% masks particularly suited to people at risk of carbon dioxide retention. Product-specific details such as connector sizes, adaptor colours and tubing are set by each manufacturer’s instructions for use, so check the packaging of the product you actually stock.
Regulatory status in the United States
The FDA product classification database lists the device under product code BYF, “mask, oxygen, low concentration, venturi”, regulated under 21 CFR 868.5600 as a Class I device (general controls). Under that regulation it is exempt from premarket notification (subpart E of part 807), subject to the limitations in 21 CFR 868.9.
Safe use and handling basics
- Use the minimum flow rate printed on the Venturi device. The BTS guideline states that this minimum is written on each device.
- Fit matters. The BTS guideline says the accuracy of oxygen delivery from a Venturi mask is greatly reduced if the mask is not accurately placed on the patient’s face.
- For a patient breathing faster than 30 breaths per minute, the guideline advises setting the flow above the minimum on the packaging (its Figure 11B shows up to 50% more).
Common mistakes
- Turning up the flow to raise the oxygen percentage. The BTS guideline states that increasing the oxygen flow rate into a Venturi mask does not increase the concentration delivered. Flow changes the total gas flow, not the percentage.
- Poor fit. A loosely placed mask reduces the accuracy of the delivered concentration.
- Ignoring the packaging minimum. Running below the stated minimum flow is outside the device’s marked use.
FAQ
What is a Venturi mask used for?
It delivers a known, fixed oxygen concentration. The BTS guideline describes it as suitable for all patients needing a known concentration of oxygen.
What concentrations does a Venturi mask deliver?
The BTS guideline lists 24%, 28%, 31%, 35%, 40% and 60%.
Does a higher flow rate give more oxygen?
No. More flow entrains more air in the same proportion, so the concentration stays the same; the guideline says increasing flow does not increase the concentration delivered.
Is a Venturi mask a regulated medical device?
In the US it is a Class I device under 21 CFR 868.5600 (FDA product code BYF), exempt from premarket notification subject to 21 CFR 868.9.
Where can I find Venturi masks and other oxygen equipment?
Browse emergency and trauma supplies.
Sources
- O’Driscoll BR et al. BTS Guideline for oxygen use in adults in healthcare and emergency settings. Thorax 2017;72:i1-i90, doi:10.1136/thoraxjnl-2016-209729. https://www.brit-thoracic.org.uk/document-library/guidelines/emergency-oxygen/bts-guideline-for-oxygen-use-in-adults-in-healthcare-and-emergency-settings/. Checked 2026-10-30.
- US FDA, Product Classification, code BYF. https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfpcd/classification.cfm?id=BYF. Checked 2026-10-30.
- 21 CFR 868.5600, Venturi mask. https://www.law.cornell.edu/cfr/text/21/868.5600. Checked 2026-10-30.
