Written and maintained by CASRAI Editorial Board
Last updated
This page describes products and general use; it is not medical advice.
An exhalation valve is a one-way valve on a respirator facepiece that lets exhaled air leave without passing back through the filter. It is used by workers, clinic staff and buyers who need to know what a valved respirator does, what it does not do, and when it is the wrong product. Most of the confusion comes from one point: a valve changes where exhaled air goes, so it changes what the respirator protects.
What an exhalation valve is
An exhalation valve opens when the wearer breathes out, so warm, moist exhaled air leaves through the valve instead of passing back through the filter media. When the wearer breathes in, the valve stays shut and all inhaled air is drawn through the filters (JSP Safety, guide to exhalation valves, checked 30 October 2026).
Who uses it: wearers of half-mask, full-face and some disposable respirators, typically in industrial and occupational settings, and the staff and buyers who select that equipment.
How it is built
The valve is made of a casing and a diaphragm. The diaphragm is a flexible membrane that opens and closes with each breath. Manufacturers describe their own designs: JSP, for example, says its Typhoon valve has overflow vents and a silicone diaphragm intended to keep performing consistently in moisture and low temperatures. That is the manufacturer’s description of its own product, not a rating that applies to every valve.
Valved and non-valved respirators
| Type | Where exhaled air goes | Source-stated use or limit |
|---|---|---|
| Respirator with exhalation valve | Out through the valve, unfiltered | Should not be used where exhaled air must be filtered (JSP Safety) |
| Half-mask and full-face respirators | Valve fitted on most | Valves are found on most of these facepieces (JSP Safety) |
| Disposable respirators | Valve fitted on some | Valves are found on some disposable respirators (JSP Safety) |
Other mask shapes you may see named alongside valved respirators, such as cup or duckbill styles, are described on the surgical mask guide.
What the valve is meant to do, and what the evidence says
JSP Safety lists these intended benefits: lower breathing resistance, lower carbon dioxide and less heat and moisture build-up inside the facepiece, and less moisture in the filters, which it says can extend filter life.
The independent evidence is more cautious. A 2012 overview by R. J. Roberge of NIOSH, published in the Journal of Occupational and Environmental Hygiene (9(11):617-623), notes that valves are said to dissipate humidity, heat and carbon dioxide, but that little research has looked at their effect on wearers. For N95 filtering facepiece respirators at low to moderate work rates, the overview reports that valves have little substantial effect on dead-space humidity, breathing rate, heart rate or core temperature, though they may lower exhalation resistance and help cool the skin under the respirator. Comfort may differ in long wear or at high work rates. The paper is from 2012 and is an overview, so it is a summary of that evidence, not a rating of any one product.
How to choose
The one selection rule a source states plainly is this: do not use a valved respirator where exhaled air must be filtered, because the valve releases unfiltered exhaled air (JSP Safety). Beyond that, follow the respirator manufacturer’s instructions and your site’s respiratory protection requirements.
Safe use and handling basics
- Check the manufacturer’s instructions for the specific respirator before use.
- Do the user seal check the instructions call for. If a respirator has an exhalation valve, a positive-pressure check may be impossible, so a negative check is used (see the N95 wearing guide).
- Where respirator choice is a lab or clinical safety decision, see the PAPR vs N95 comparison.
Common mistakes
- Treating a valved respirator as if it protected people around the wearer. The valve releases unfiltered exhaled air, so it is not for situations that require exhaled air to be filtered.
- Assuming a valve makes the respirator more comfortable in every setting. The 2012 NIOSH overview found little substantial effect on several physiological measures at low to moderate work rates.
Other devices use the same term
Ventilators, anaesthesia breathing circuits and CPAP masks also contain parts called exhalation valves. They are different devices with different functions and are not covered here. For a related ventilation valve, see the PEEP valve guide and the Passy-Muir valve guide.
FAQ
What does an exhalation valve do on a respirator?
It opens as you breathe out so exhaled air leaves through the valve rather than back through the filter, and it closes as you breathe in so inhaled air is drawn through the filters (JSP Safety, checked 30 October 2026).
Does a valved respirator filter the air I breathe out?
No. The valve releases exhaled air unfiltered, so it should not be used where exhaled air must be filtered (JSP Safety).
Does an exhalation valve make a respirator cooler?
Manufacturers say valves reduce heat and moisture. A 2012 NIOSH overview found little substantial effect on core temperature at low to moderate work rates, with possible skin cooling (Roberge 2012).
Sources
- JSP Safety, “Guide to Exhalation Valves”, https://jspsafety.helpjuice.com/en_GB/guide-to-exhalation-valves (manufacturer help page, checked 30 October 2026).
- Roberge RJ, “Are exhalation valves on N95 filtering facepiece respirators beneficial at low-moderate work rates: an overview”, J Occup Environ Hyg 2012;9(11):617-623, NIOSH, https://stacks.cdc.gov/view/cdc/194062 (abstract checked 30 October 2026).
