December 10, 2020

NIOSH Study Examines Potential for Source Control of FFRs with an Exhalation Valve

Filtering facepiece respirators (FFRs) with an exhalation valve can reduce particle emissions to levels “similar to or better than those provided by surgical masks, procedure masks, or cloth face coverings,” NIOSH’s National Personal Protective Technology Laboratory has found. NPPTL’s findings are based on the results of tests of 13 FFR models from 10 different manufacturers, and are described in a technical report published on Dec. 9. NIOSH’s research stems from questions raised by the COVID-19 pandemic regarding the effectiveness of using an FFR with an exhalation valve for source control. A concern is that these respirators may allow unfiltered, exhaled air to pass through the valve, which would mean that they may not offer source control to protect others in case the wearer is infected with SARS-CoV-2. NPPTL’s study finds that modifications to these respirators can further reduce particle emissions, and that securing an electrocardiogram (ECG) pad or surgical tape over the valve from the inside of the respirator “can provide source control similar to that of an FFR with no exhalation valve.”

Current CDC guidance states that individuals should wear a respirator without an exhalation valve when both source control and respiratory protection are required. In situations where source control is needed and only a respirator with an exhalation valve is available, the agency advises wearers to cover the valve with a surgical mask, procedure mask, or cloth face covering that does not interfere with the fit of the respirator. Of the mitigation strategies examined during the NPPTL study, covering the FFR with a surgical mask was not the most effective. Researchers found that covering the exhalation valve inside the FFR with an ECG pad was the best mitigation strategy, with the strategy of securing surgical tape over the exhalation valve inside the FFR performing nearly as well.

NPPTL’s technical report explains that workers who need respiratory protection and are concerned about source control can turn to FFRs with an exhalation valve as an additional source of equipment during respirator shortages.

“These [study] results represent one of the first measurements of particle penetration through FFRs with an exhalation valve that are tested in an outward position, and the findings have important implications for guidance on source control and mitigation,” the report concludes.

The full report is available for download from NIOSH’s website.