Oxygen equipment has two separate parts: the source supplies gas, and the interface delivers it to the person. A concentrator or cylinder is a source. A nasal cannula, simple mask, reservoir mask or Venturi mask is an interface. Choosing one does not determine the correct setting for the other.
This guide explains the differences so that a prescription and equipment demonstration are easier to follow. It is not a table for selecting an emergency treatment or changing an interface at home.
Nasal cannula
A conventional cannula has two small prongs at the nostrils. The face remains open, which can help with talking, eating and longer use. Oxygen mixes with room air as the person breathes, so the inspired concentration varies with breathing pattern and the setup.
The actual cannula must suit the prescribed flow, size and intended use. A standard cannula is not the same equipment as a heated high-flow nasal system. Mouth breathing alone does not establish that a cannula has stopped delivering useful oxygen.
Simple face mask
A simple mask covers the nose and mouth and has openings through which exhaled gas can leave. Its output concentration is variable. Sufficient oxygen flow is needed to clear exhaled gas, so running it below its specified minimum can be unsafe.
Adult guidance commonly describes a 5–10 L/min range for a conventional simple mask, but the exact interface instructions and prescription govern use. That range is not a recommendation to increase anyone’s oxygen to fit a mask they happen to own.
Reservoir or non-rebreather mask
This mask includes a reservoir bag and a valve arrangement designed for high-concentration delivery. It is commonly used in acute care, where supply, bag behaviour, fit and the patient’s condition can be assessed by trained staff.
It is not a general upgrade for a home cannula. The source must meet the requirements of the particular mask, and a clinical plan must cover its use and escalation. A 5 LPM concentrator label does not establish compatibility with every reservoir mask.
Venturi mask
A Venturi system draws room air into the oxygen stream through a calibrated adapter to provide a selected concentration under its specified conditions. The adapter’s stated oxygen flow and unobstructed air-entrainment openings matter.
Do not identify a setting by colour alone: read the concentration and instructions on the actual adapter or packaging. An obstructed opening, incorrect assembly or inadequate total gas delivery can undermine the intended performance. The treating team sets the prescription and assesses the response.
High-flow and breathing-support systems
Heated high-flow nasal therapy uses specialised equipment and is different from simply turning up a conventional cannula. Positive-airway-pressure and ventilation systems also have distinct functions. None should be assembled from generic accessories or substituted on the basis of this comparison.