The Need for Fit Testing During Emerging Infectious Disease Outbreaks

Posted on by Maryann M. D’Alessandro, PhD; LT Megan Casey, RN, BSN, MPH; and Jaclyn Krah Cichowicz, MA

Proper respirator use is essential for healthcare workers who are expected to interact with patients with infectious respiratory diseases. The Occupational Safety and Health Administration (OSHA) requires healthcare facilities to maintain a respiratory protection program that specifies requirements such as annual fit testing, medical clearance, and training. Initial fit testing is required before using a respirator. In addition to annual fit testing, fit testing is required when there are changes in an employee’s physical condition that could affect respirator fit and when a worker must wear a new model or type of tight-fitting respirator, such as the common N95® filtering facepiece respirator. However, during an infectious disease outbreak, such as coronavirus disease 2019 (COVID-19), when there are many other demands upon your time, and resources are being conserved, it is natural to ask – is all this fit testing really necessary?

The Purpose of Fit Testing

Fit testing confirms the fit of any respirator that forms a tight seal on the user’s face before it is used in the workplace. This ensures that users are receiving the expected level of protection by minimizing contaminant leakage into the facepiece. When a respirator does not fit properly, a portion of the air you breathe can bypass the respirator’s filter and enter your breathing airstream through breaks in the seal of the respirator along your face. If this happens, you may be exposed to harmful pathogens in the environment. In a similar vein, it is important to wear the respirator at all times during the exposure because even short periods of exposure substantially reduces your protection. This all boils down to a simple reality: if the respirator does not form a seal with the face, it cannot provide the expected level of protection. Therefore, fit testing at all the OSHA-required times is necessary – however, during large-scale infectious disease outbreaks, there are ways to save time when fit testing as well as conserve supplies. NIOSH  encourages facilities to take the necessary steps to ensure fit testing is conducted in compliance with OSHA protocols.*

Note: OSHA issued Temporary Enforcement Guidance – Healthcare Respiratory Protection Annual Fit Testing for N95 Filtering Facepieces During the COVID-19 Outbreak on March 14, 2020. This temporary enforcement guidance suspends the annual fit testing requirement of N95 filtering facepiece respirators. However, initial fit tests for healthcare personnel with the same model, style, and size respirator are still required. The temporary enforcement guidance on OSHA’s website.

Fit Test Methods

There are two methods of fit testing – quantitative and qualitative. A quantitative fit test uses an instrument to numerically measure the effectiveness of the respirator. A qualitative fit test is a pass/fail test that relies on the individual’s sensory (taste or smell) detection of a test agent such as Saccharin (sweetener) or Bitrex® (bitter) solutions. These methods are described in the OSHA regulations and in the Hospital Respiratory Protection Program Toolkit.

Regardless of which type of fit test is used in your facility’s respiratory protection program, a successful fit test only qualifies you to use the specific brand/make/model and size of respirator that you wore during that test. Respirator sizing is not standardized across models or brands. Do not assume that because you passed a fit test wearing a size medium in one model, a medium of another model or brand will have an equivalent fit: this could result in an improperly fitted respirator and potentially harmful exposure to airborne pathogens.

Fit Testing Considerations for Conserving Time and Supplies

With the global impact of COVID-19, qualitative fit testing is the preferred method of fit testing to help slow the depletion of the inventory of N95 respirators, because the respirator used for a qualitative fit test can be worn again after the test. (Quantitative fit testing requires a hole to be punched in the respirator and therefore it must be disposed of after the test.) However, a disadvantage of qualitative fit testing is that the test procedure is frequently administered incorrectly and relies on the wearer to report tasting a challenge solution, either a Saccharin (sweetener) or Bitrex® (bitter) solution, to indicate that a respirator does not properly fit. In these cases, poorly fitting respirators may still pass the fit test. Therefore, it is crucial that the operators** carrying out these fit tests are well-trained and highly proficient.

For healthcare systems currently using quantitative fit test methods, considerations can be made to switch to qualitative fit test methods to minimize the destruction of N95 respirators. Any switch in methods should be assessed to ensure aptitude of the fit test operators carrying out the test.

Healthcare facilities should begin training and implementing a plan for fit testing immediately. It is essential to have healthcare professionals trained and fit tested prior to receiving COVID-19 patients.  For locations where the surge has not arrived and experienced fit tester operators are lacking, begin comprehensive training now.*


Just-In-Time Fit Testing

A typical qualitative fit test should take between 15-20 minutes. However, during an outbreak, even 15-20 minutes per employee can be difficult to achieve, especially for large facilities who may need to fit test a significant number of workers who are not required to wear respirators during times of normal operation because their job does not typically place them at risk for exposure to airborne infectious diseases.

Determining the number of operators depends on the number of fit tests that need to be completed and the amount of time available. A highly experienced fit testing operator can complete about three fit tests per hour. So, one operator working 40 hours a week for one week can complete 120 tests (40hrs * 3 tests/hr = 120 tests per week). It is also helpful to have an additional person assist with logistics, recordkeeping, and management of the equipment. If you don’t have this “additional person”, the number of fit tests will be less.*

During public health emergency responses only, facilities may elect to implement the “just-in-time” method for fit testing. This method has been incorporated into pandemic plans for many facilities. Just-in-time fit testing is a way to fit test large numbers of workers at one time. An experienced fit test operator may be able to fit test a maximum of five people simultaneously. This method works by having a fit test operator fit test five people, while simultaneously training them to also be fit operators. Those five people can then conduct fit tests for the remaining staff. The result is six operators fit testing up to five people each, thereby completing fit testing for 30 people every 20 minutes, or up to 60 people per hour. Using this method, over 400 people may be tested in one eight-hour day. If multiple people are being fit tested at once, or if fit testing is occurring without significant breaks, it is essential to have additional staff assist with logistics, recordkeeping and management of the equipment.

While the just-in-time method could be useful during a pandemic, this process has not been validated within peer-reviewed publications and may differ from facility to facility. Additionally, the training obtained for just-in-time fit testing during a pandemic is for use during the response only. If those trained during a response wish to continue acting as a fit test administrator during time of regular operation, they should go through the standard training of their respiratory protection program. Even during a stressful response effort, training is vital and should be conducted by those with the most experience. For a train-the-trainer checklist, see the Implementing Hospital Respiratory Protection Programs: Strategies from the Field. *

Fit Testing Kits: Improving the Administration of Qualitative Fit Testing

With an increase in the number of employees requiring fit testing, healthcare facilities understandably have questions about being prepared with the appropriate number of fit testing kits. The first thing to understand is that the number of fit testing kits purchased should not be based on the number of fit tests that can be conducted per kit. The number of tests is primarily limited by the amount of fit testing solution available. Many suppliers provide kits using Saccharin and Bitrex® in a 55ml bottle of strong solution. A 55ml bottle is advertised to test 150 people. However, nebulizers need to be emptied, rinsed, and refilled every 4 hours; this decreases that number significantly and facilities should consider ordering extra solution.

Generally speaking, the number of kits purchased can be determined based on three factors:

  1. The number of people who need to be fit tested
  2. The number of fit tests that need to be conducted in a given period of time
  3. The number of fit test operators who will be using the kits simultaneously

Consider that not everyone will pass the fit test the first time, re-testing with different models and sizes will consume more time and solution. In addition, it is recommended that you purchase a second enclosure (hood) for each kit you purchase. One hood is dedicated for the weaker sensitivity solution, the other is dedicated for the stronger fit test solution. For specific questions about your qualitative fit testing needs, contact the manufacturer of the supplies you plan to use.

Facial Hair and Fit Testing

Facial hair is a common frustration when it comes to fit testing employees who aren’t accustomed to wearing tight-fitting respirators on a regular basis. However, the facts are straightforward; facial hair that lies along the sealing area of a respirator will cause a respirator to leak. The presence of facial hair under the sealing surface causes 20 to 1000 times more leakage compared to clean-shaven individuals.[1] Facial hair that does not lie along the sealing area of the respirator is considered acceptable.

A facility may consider loose-fitting powered air purifying respirators (PAPRs) as an alternative for employees who are unwilling or unable to shave for both the fit test and during respirator use. This type of respirator uses a battery-powered blower to force air through a particle filter for the wearer to breathe. They are capable of filtering particles from the air at efficiencies suitable to be substituted in situations in which an N95 respirator has been recommended. Loose-fitting PAPRs, in which the hood or helmet is designed to form only a partial seal with the wearer’s face, or hoods that seal loosely around the wearer’s neck or shoulders, do not require fit testing. PAPRs also provide the added benefit of being reusable and therefore conserving supplies of N95 respirators.

For additional information, please consult the CDC respirator use guidance for healthcare professionals for COVID-19:


Maryann M. D’Alessandro, PhD, is the Director of the NIOSH National Personal Protective Technology Laboratory.

LT Megan Casey, RN, BSN, MPH, is a Nurse Epidemiologist in the NIOSH National Personal Protective Technology Laboratory.

Jaclyn Krah Cichowicz, MA, is a Health Communications Specialist in the in the NIOSH National Personal Protective Technology Laboratory.

Resources on Fit Testing

How to Properly Put on or Take off a Disposable Respirator (Instruction sheet)

Filtering out Confusion: Fit Testing (Fact Sheet)

Filtering out Confusion: User Seal Check (Fact Sheet)

To Beard or not to Beard, That’s a Good Question (Blog)


* Text added on 4/17/20  for clarification.

** “Administrator” changed to “operator” throughout document to avoid confusion with respiratory protection program administrators (4/17/20)


N95 is a certification mark of the U.S. Department of Health and Human Services (HHS) registered in the United States and several international jurisdictions.

Bitrex is a registered trademark of Macfarlan Smith Ltd.



[1] Stobbe TJ, daRoza RA, Watkins MA [1988]. Facial hair and respirator fit: a review of the literature. Am. Ind Hyg Assoc J. 49(4):199-204.


The Centers for Disease Control and Prevention is addressing questions related to the Coronavirus Disease 2019 through CDC-INFO and on their webpage. As such, this blog has been closed to comments. Please visit You can find the most up-to-date information on the outbreak and get the latest answers to frequently asked questions. If you have specific inquiries, please contact CDC-INFO at or by calling 800-232-4636. If you have questions about PPE that are not related to Coronavirus Disease 2019, please contact us at

Posted on by Maryann M. D’Alessandro, PhD; LT Megan Casey, RN, BSN, MPH; and Jaclyn Krah Cichowicz, MA
Page last reviewed: February 20, 2024
Page last updated: February 20, 2024