Written and maintained by CASRAI Editorial Board
Last updated
This page describes products and general information; it is not medical advice.
A simple face mask is an oxygen mask with side holes and no reservoir bag, and the flow range stated for it in clinical references is 5 to 10 L/min. This page is for clinic staff, buyers and students who want to know where that range comes from, what concentration it is described as delivering and how the mask differs from a nasal cannula and a reservoir mask. Which device and setting suit a particular person is decided by the treating clinician, not by this page.
What flow range is stated for a simple face mask?
Three references agree on the range. The British Thoracic Society (BTS) emergency oxygen guideline lists a simple face mask at 5-10 L/min. The Thoracic Society of Australia and New Zealand (TSANZ) acute oxygen guideline states that a simple face mask can deliver an FiO2 of 0.35-0.60 at an oxygen flow of 5-10 L/min. StatPearls (NCBI Bookshelf, last updated January 22, 2025) describes simple face masks as low-flow systems that provide oxygen at rates of 5 to 10 L/min. The mask maker’s instructions for use remain the reference for any specific product.
Why the stated minimum is 5 L/min
A simple face mask has side holes and no reservoir bag, so the mask body holds exhaled gas. TSANZ states that for simple face masks, flow rates of below 5 L/min should be avoided because of the potential risk of carbon dioxide rebreathing (Grade C recommendation). This is the main design difference from a nasal cannula, which TSANZ lists as having no risk of rebreathing of carbon dioxide and which is described at lower flows.
Oxygen concentration at 5-10 L/min
Published figures differ slightly. TSANZ states an FiO2 of 0.35-0.60 for a simple face mask at 5-10 L/min. StatPearls gives approximately 40% to 60%. Both describe a range, not a fixed value. StatPearls notes, in its discussion of nasal oxygen, that FiO2 depends on the breathing rate and tidal volume because supplemental oxygen mixes with room air, and the same low-flow mixing applies to open-sided masks. StatPearls also states that simple face masks cannot deliver 100% oxygen without a tight seal. The BTS text does not give a percentage for the simple mask, so this page does not attribute one to BTS.
Simple mask vs nasal cannula vs reservoir mask
| Device | Flow range stated | Concentration stated | Source |
|---|---|---|---|
| Nasal cannula | 1-4 L/min (TSANZ); 1-6 L/min (StatPearls) | FiO2 0.24-0.35 (TSANZ); about 24-40% (StatPearls) | TSANZ, StatPearls |
| Simple face mask | 5-10 L/min | FiO2 0.35-0.60 (TSANZ); about 40-60% (StatPearls) | BTS, TSANZ, StatPearls |
| Reservoir (non-rebreather) mask | 15 L/min (TSANZ, BTS); 10-15 L/min (StatPearls) | FiO2 0.6-0.8 (StatPearls) | TSANZ, BTS, StatPearls |
StatPearls describes the non-rebreather as a simple mask connected to a small reservoir bag through one-way valves. See the separate guides on the non-rebreather mask, the nasal cannula and the Venturi mask, which delivers a controlled concentration rather than a variable one. For cannula flow ranges in more detail, read the nasal cannula oxygen delivery flow rate and sizing guide.
Who uses it
Nurses, paramedics, respiratory therapists and physicians in emergency, ward and prehospital care use simple face masks; buyers and stores staff stock them as part of oxygen delivery kits. A mask is normally connected to a flow source with oxygen tubing. For mask styles used with CPAP, see the guide to CPAP and oxygen mask types.
Handling basics
- Check the flow range printed in the manufacturer’s instructions for use; the guideline range above is a general reference only.
- Because the delivered concentration varies with breathing pattern and mask fit, it is not read from the flow setting alone.
- Single-use masks are discarded after use according to local policy.
Frequently asked questions
What is the flow rate for a simple face mask?
The stated range is 5-10 L/min in BTS, TSANZ and StatPearls. TSANZ states that flows below 5 L/min should be avoided because of rebreathing risk.
What oxygen percentage does a simple face mask deliver?
About 35-60% depending on the source (TSANZ 0.35-0.60; StatPearls approximately 40-60%), varying with breathing rate, tidal volume and fit.
How does a simple face mask differ from a reservoir mask?
A reservoir (non-rebreather) mask is described by StatPearls as a simple mask connected to a small reservoir bag through one-way valves, and it is listed at higher flows and higher concentrations in the table above.
Can a simple face mask deliver 100% oxygen?
No. StatPearls states simple masks cannot deliver 100% oxygen without a tight seal and are low-flow systems.
Related supplies, such as elastic bandages, are sold in separate medical supply categories.
Sources
- O’Driscoll BR et al. BTS Guideline for oxygen use in adults in healthcare and emergency settings, summary of recommendations. Thorax 2017;72(Suppl 1):ii1-90. https://www.brit-thoracic.org.uk/document-library/guidelines/emergency-oxygen/bts-guideline-for-oxygen-use-in-healthcare-and-emergency-settings-summary-of-recommendations/. Checked 2026-10-30.
- Thoracic Society of Australia and New Zealand, oxygen guidelines for acute oxygen use in adults. https://pmc.ncbi.nlm.nih.gov/articles/PMC4654337/. Checked 2026-10-30.
- StatPearls, Oxygen Therapy (last updated January 22, 2025). https://www.ncbi.nlm.nih.gov/books/NBK551617/. Checked 2026-10-30.
