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Use of Thin Dressings Under N95 Respirators: Exploring Their Effect on Quantitative Fit Testing Results to Guide Hospital Practice During the COVID-19 Pandemic

Case Report

Use of Thin Dressings Under N95 Respirators: Exploring Their Effect on Quantitative Fit Testing Results to Guide Hospital Practice During the COVID-19 Pandemic

Index: Wound Management & Prevention 2020;66(11):13–17 doi: 10.25270/wmp.2020.11.1317


At the beginning of the coronavirus disease-19 pandemic, health care staff at a level 1 trauma center in the state of New York experienced facial irritation and skin breakdown under their N95 respirators due to increased and prolonged use. PURPOSE: Members of the Certified Wound and Ostomy Nurse, Nurse Practitioners staff were charged with developing recommendations within 48 hours to help prevent and manage facial skin issues using available products that would not compromise the seal of the respirators. METHOD: With the assistance of a health care safety specialist from the Environmental Health and Safety Department of the hospital, an ambient particle counting device was used to measure the N95 fit factor following application of a liquid skin barrier, transparent film dressing, light silicone-based adhesive dressing, or an extra-thin hydrocolloid dressing on the bridge of the nose and the cheekbones underneath an N95 respirator of 2 hospital staff members who volunteered to test the dressings. RESULTS: All thin dressings tested showed a fit factor over 100, reflecting an effective seal. The highest fit factors were seen with the liquid skin barrier in the 2 volunteers (200 and 198, respectively). Thin dressing usage information was included in the hospital guidelines for N95 respirators and shared with staff.  Subsequent feedback suggests that the light silicone-based adhesive dressing and the extra-thin hydrocolloid dressing were preferred. CONCLUSION: Thin dressing use may help reduce skin complications among hospital staff during periods of extended N95 respirator wear time. Because use of the dressings did not result in failure of the quantitative fit test, they were permitted for use by health care staff under their N95 respirators. Studies are needed to help health care facilities optimize N95 respirator use to protect staff from coronavirus disease-19 and respirator-related skin complications while supply shortages remain. 


During the early stages of the coronavirus disease-19 (COVID-19) pandemic in 2020, frontline hospital staff at Stony Brook University Hospital (SBUH), a 624-bed teaching hospital and level 1 trauma center in the state of New York, began to report facial skin breakdown under their N95 respirators. SBUH required staff to wear N95 respirators/facial protective equipment (FPE) for personal protection at all times while caring for patients diagnosed with COVID-19. Initiation of this mandate resulted in FPE wear time for the entire duration of staff member shifts. Members of the SBUH Certified Wound and Ostomy Nurse (CWON), Nurse Practitioners (NPs) staff were charged by the chief nursing officer to develop FPE respirator-related skin irritation prevention and treatment recommendations for the health care staff. The recommendations were needed within 48 hours and were to be limited to products already on the hospital formulary. 


Three (3) guidelines for protecting the skin under N95 respirators/FPE,1–3 were reviewed. All 3 recommended applying a liquid skin sealant prior to donning FPE as both a preventive measure for, and treatment of, skin breakdown.1–3 Applying thin, prophylactic dressings under FPE was described as a possible mitigation for skin injury but was proposed with caution because of the lack of evidence-based information to ensure uncompromised respirator fit and seal.1–3

The CWON NPs contacted SBUH’s Environmental Health and Safety (EHS) Department for assistance in determining how best to test the seal of the N95 respirators while using facial dressings. There are 2 methods of respirator fit testing used in health care institutions, qualitative and quantitative.4 Qualitative fit testing is a pass/fail method using one’s sense of taste, smell, or reaction to an irritant to detect leakage into the respirator but does not measure the amount of leakage. Quantitative fit testing uses a machine and probe attached to the respirator to measure the amount of leakage into the respirator and does not rely on an individual’s senses. Both methods are accepted by the Occupational Safety and Health Administration.4 SBUH used the quantitative method when fit testing N95 respirators.

A healthcare specialist from the EHS Department performed quantitative fit testing using the N95 respirators (Health Care Particulate Respirator and Surgical Mask [product numbers 1860 regular and 1860S small]); 3M, St. Paul, MN) on 2 healthy members of the health care staff who had different facial structures. The fit testing process used the PortaCount Pro+ Respirator Fit Tester 8038 (TSI, Shoreview, MN), which is an ambient particle counting device that provides quantitative assessments of face seal leakage5 (Figure 1). Use of this device is an accepted fit test method by the American National Standards Institute6; Canadian Standards Association7; Health and Safety Executive8;  and Occupational Safety and Health Administration4 for all tight-fitting respirators. The healthcare safety specialist fitted the N95 respirator with a probe, which was connected to the fit testing unit via a tube. The probe was installed using a sharp tool that pierces the N95 and “loads” the probe within the “breathing zone” of the respirator, which is usually in the center, between the person’s nose and mouth (Figure 2).5

The device fit-tests the person wearing the respirator while he or she performs the following exercises: breathing normally, breathing deeply, moving the head side to side, moving the head up and down, talking, grimacing, bending at the waist, and repeating normal breathing. The device calculates a fit factor grade for each of these exercises and an overall fit factor grade for all the exercises combined.5 

The fit factor is the ratio of the number of particles measured inside and outside the respirator. It is the numerical result of the quantitative fit test performed on a respirator’s facepiece and indicates the effectiveness of the seal against the individual’s face. It is expressed as a ratio that identifies how many times “cleaner” the air inside the respirator’s facepiece is compared with the air outside the facepiece. The acceptable fit factor for an N95 respirator is 100 or higher.5 

Testing was performed using a liquid skin barrier (Cavilon Advanced Skin Protectant; 3M) as the control product, a transparent film dressing (Tegaderm; 3M), a light silicone-based adhesive dressing (Mepilex Lite; Mölnlycke Health Care, Gothenburg, Sweden), and an extra-thin hydrocolloid dressing (DuoDerm Extra Thin; ConvaTec, Bridgewater Township, NJ). 

The CWON NPs sent out an emergency, high-priority email questionnaire to obtain feedback about the most common location of skin issues from wearing an N95 mask; the most reported locations were the bridge of the nose and cheekbones. Therefore, the dressings used for testing were placed on the face in those areas (Figure 3). 

The dressings were cut into rectangles and applied as follows: a 2.5 cm × 6 cm piece was placed on the bridge of the nose, while a 2.5 cm × 2.5 cm piece was placed on each cheekbone. Dressings were placed to sit under the edges of the N95 respirator, and size and placement were consistent with each dressing type on both test subjects with no dressing overlap. Dressings were gently removed between testing without adhesive removers. The testing procedure took approximately 20 to 30 minutes per dressing for each individual, allowing approximately 5-minute intervals between each test. Each participant used the same respirator for all dressings. Participant 1 used the 1860S (small) respirator, and participant number 2 used the 1860 (regular) respirator. Both participants agreed to participate, and participant 1 gave her permission for her photographs to be used in this publication. 


Fit test findings are shown in Table 1. A fit factor of 100 or higher reflects an effective seal, with a grade of 200+ reflecting maximum fit.5 Participant 2 had a larger nasal bridge than participant 1. It was noted that participant 2’s individual fit factor numbers were lower than those recorded for participant 1. Based on the fit factor scores, both participants had an adequate, protective seal with the N95 respirator, regardless of protective dressing or product used.  However, the highest fit factor for both participants was achieved using the liquid skin barrier only.

Using the fit factor testing results, the CWON NPs developed a product recommendation chart that included all products used, product ordering information, proposed degree of padding, and total fit factor scores from the testing. The chart included recommended measurements and facial placement of the dressings. The CWON NPs recommended that the liquid skin barrier be applied under the thin dressings to offer further skin protection. The product recommendation chart was sent via email to all staff. Nursing units throughout the hospital placed the chart in common areas so that it was accessible to all staff. 


Based on staff feedback, which was requested and received via email, the light silicone-based adhesive dressing and the extra-thin hydrocolloid dressing were preferred and successfully incorporated into the hospital respirator-related skin breakdown prevention practice over several months. Although liquid skin barrier and transparent film dressings were also available, staff members reported that they did not frequently choose these products because they did not reduce injury or discomfort from existing skin breakdown. Staff members reported use of the liquid skin barrier underneath the thin dressings. 

It was determined that it was possible to achieve an acceptable fit-test seal with the use of thin dressings under the N95 respirators. This permitted health care staff to use the thin dressings of their choice to prevent and/or treat any skin breakdown and discomfort on the bridge of the nose and cheekbones. The CWON NPs were informed by hospital administration that the staff positivity rate remained equal to the overall community rate. There was no spike in the number of COVID-19-positive cases among the hospital’s health care workers after initiating use of thin dressings under the N95 respirators. 

Considering ongoing supply constraints, SBUH is considering the evaluation of different systems to disinfect N95 respirators for reuse should the need arise. The N95 respirators become soiled when in contact with makeup, facial creams, and ointments, eliminating the ability to disinfect them. Prohibiting their use by hospital staff who need to use N95 respirators adds to the challenge of providing skin care recommendations. It is also unknown if the use of liquid skin sealants and dressings affect the ability to disinfect these masks and/or their integrity.  


Two (2) subjects with different facial structures were evaluated. The sample size was limited because the recommendations were needed quickly and because the quantitative fit testing procedure destroys the mask during the process. N95 respirator supplies were limited due to the pandemic. This article is for informational purposes only, and health care facilities are urged to use their own clinical judgement in making recommendations to their staff. The evaluation, which should not be considered a research study, was completed under the stress of a pandemic and at a time when recommendations were needed in an emergency situation.

Because there is a range of variables involved, considerations for future evaluations or research should include institutional review board approval of a randomized clinical study with a larger sample size that incorporates a diverse group of facial shapes, N95 respirator types, and sizes/shapes of thin film dressings. 


This evaluation was completed during a public health emergency to determine if the placement of certain thin dressings used under N95 respirators would interfere with the N95 respirator seal needed to protect health care staff from exposure to COVID-19. Quantitative fit testing showed an adequate seal with the thin dressings that were tested. This evaluation also confirmed recommendations made in the professional guideline documents reviewed that a liquid skin barrier could be used under the N95 respirator without disruption of the facial seal. The evaluation lends support to the possible mitigation of skin injury with thin dressing use, but this could not be confirmed or refuted because of the small number of participants.


The authors thank Healthcare Safety Specialist Ellen O’Hare, Stony Brook University Hospital, Stony Brook, New York. 


Ms. Guschel, Ms. Chmiel, and Ms. Rosenstein are certified adult nurse practitioners and certified wound and ostomy nurses at Stony Brook University Hospital, Stony Brook, NY. Address all correspondence to Susan Guschel, MS, ANP-C, CWON, Stony Brook University Hospital, 101 Nichols Road, Stony Brook, NY 11794; tel: (631) 444-7531; email:

Potential Conflicts of Interest

None disclosed.