Over three million American workers are required to wear respirators to protect themselves from hazards in their workplace. Since the fit of the respirator to the user’s face affects the protection provided by the respirator, occupational safety and health professionals recommend fit assessment during the initial selection of a respirator model and at some periodicity as part of a respiratory protection program. In 1998, the Occupational Safety and Health Administration (OSHA) adopted new requirements for occupational respiratory protection programs requiring respirator users to receive training and pass a fit test before using a respirator, and annually thereafter (29 Code of Federal Regulations Section 1910.134), based on current ANSI standards and public comments citing workplace experience.
Fit testing is the only accepted way to determine if the respirator fits properly. Periodic testing is needed to ensure the fit continues to be acceptable. One position is that annual retesting of respirator fit is needed to detect, at an early stage, the percentage of respirator users whose respirators no longer fit them properly. Another perspective argues that fit testing should be required only when an employee switches to a different respirator or when a significant change occurs in an individual’s physical condition which may interfere with obtaining an adequate faceseal.
The current fit test requirements and their rationale were questioned at the 2004 Centers for Disease Control and Prevention Workshop on Respiratory Protection for Airborne Infectious Agents in Atlanta, Georgia where participants called for the quantification of the benefit and the scientific validity of annual fit testing. Participants questioned whether annual fit testing must be performed in the same entirety and manner as initial fit testing and asked if annual fit testing could be redesigned to only verify proper donning of the respirator and acceptability of fit. The workshop also highlighted the need to quantify the role of weight loss or gain on fit testing.
In the 2007 Institute of Medicine (IOM) report, Assessment of the NIOSH Head and Face Anthropometric Survey of U.S. Respirator Users, the IOM recommended that “NIOSH [...] perform research to determine which facial features have the greatest impact on respiratory protection of face masks in the workplace, using quantitative measures.”
To address many of the questions surrounding the periodicity of respirator fit testing, NIOSH is proposing a first-of-its-kind study that will assess respirator fit and facial dimension changes as a function of time for a representative sample of subjects wearing filtering-facepiece respirators (see the study protocol). NIOSH will recruit 220 study participants (subjects) representative of the U.S. workforce and distributed across the 10 face size categories of face width and face length. For each participant, NIOSH will collect a set of 13 traditional face measurements, height, weight, and a scanned image using a Cyberware Model 3030 head scanner at the onset of the study and every six months thereafter for three years.
Subjects will be required to pass a respirator fit test for inclusion in the study. All participants will be retained in the study regardless of subsequent changes in fit. The rate at which respirator fit changes as a function of time will be determined. Possible relationships between physical changes and changes in respirator fit will also be investigated. Knowledge gained from this research will be used to formulate hypotheses for additional studies to further explore questions surrounding the periodicity of respirator fit testing.
Some further questions for consideration in the protocol include, but are not limited to, the following:
- Should subject/respirator combinations be limited to only those which initially provide appropriate protection?
- What, if any, additional information regarding change in fit over time would be obtained by including subjects fitted with multiple respirator models?
- Should NIOSH ensure the fitted respirator models include all types (cup, duckbill, flatfold, etc.) of filtering facepiece respirator designs?
The study is currently in the early stages of development. We would appreciate input to further inform the research as we proceed. Please provide comments on the study and methodology through the NIOSH Science Blog before June 1, 2008. This study is part of the NPPTL Facial Anthropometrics Research Roadmap.
—Ed Fries and Ziqing Zhuang
Mr. Fries is an engineer in the NIOSH National Personal Protective Technology Laboratory (NPPTL) Office of the Director and serves as the Assistant Coordinator for the NIOSH PPT Program.
Dr. Zhuang is a senior researcher in the Technology Research Branch at the NIOSH National Personal Protective Technology Laboratory.