The authors have declared that no competing interests exist.
During the course of the COVID-19 pandemic, there have been suggestions that various techniques could be employed to improve the fit and, therefore, the effectiveness of face masks. It is well recognized that improving fit tends to improve mask effectiveness, but whether these fit modifiers are reliable remains unexplored. In this study, we assess a range of common “fit hacks” to determine their ability to improve mask performance.
Between July and September 2020, qualitative fit testing was performed in an indoor living space. We used quantitative fit testing to assess the fit of both surgical masks and KN95 masks, with and without ‘fit hacks’, on four participants. Seven fit hacks were evaluated to assess impact on fit. Additionally, one participant applied each fit hack multiple times to assess how reliable hacks were when reapplied. A convenience of four participants took part in the study, three females and one male with a head circumference range of 54 to 60 centimetres.
The use of pantyhose, tape, and rubber bands were effective for most participants. A pantyhose overlayer was observed to be the most effective hack. High degrees of variation were noted between participants. However, little variation was noted within participants, with hacks generally showing similar benefit each time they were applied on a single participant. An inspection of the fit hacks once applied showed that individual facial features may have a significant impact on fit, especially the nose bridge.
Fit hacks can be used to effectively improve the fit of surgical and KN95 masks, enhancing the protection provided to the wearer. However, many of the most effective hacks are very uncomfortable and unlikely to be tolerated for extended periods of time. The development of effective fit-improvement solutions remains a critical issue in need of further development.
During the COVID-19 pandemic, shortages of personal protective equipment (PPE) have resulted in members of the public having no choice other than to wear poorly fitting face masks, including surgical and KN95 masks, which are the focus of this study. Proper fit has been noted as a primary factor in determining the effectiveness of face masks, but the masks available to the public often suffer from poor fit [
There are two key factors that determine mask effectiveness: the filtration efficiency of the mask material and the fit of the mask. Better fitting masks offer fewer gaps between the wearer’s face and the edges of the mask, ensuring that inhaled air is actually filtered. Air tends to take the path of least resistance; therefore, if there are small gaps around a high resistance mask, air will tend to travel through them, thus bypassing filtration of the mask material [
Unfortunately, little research has been done to assess the effectiveness of these techniques. Early research, seeking to validate a protocol for measuring mask performance, has suggested that a nylon over-layer worn over a face covering may enhance the performance of masks. However, the same data also suggests that improvement techniques may heterogeneously affect different types of face coverings [
There are two established methods used to assess the fit of face masks: quantitative fit testing and qualitative fit testing [
During quantitative fit testing, air samples are taken to continuously measure the concentrations of particles both inside and outside of a donned mask. The concentration of particles outside the mask are compared via an industry standard formula, to generate a fit factor score [
CB = concentration B, concentration outside the mask before the respiratory sample
CA = concentration A, concentration outside the mask after the respiratory sample
CR = concentration R, concentration inside the mask
This fit factor is a numerical score of how well the mask fits the wearer; meaning the fewer particles that make their way into the mask, the better the fit. As fit factor is particle concentration outside divided by particle concentration inside, a mask with a fit factor of 100 provides air 100 times cleaner than outside air and a mask with a fit factor of 10 provides air 10 times leaner than the outside air [
Quantitative fit tests were conducted using a Portacount, TSI, Minnesota, model 8038+ capable of evaluating masks with less than 99% efficiency [
Four participants took part in the study, three female and one male. Ethical approval for this study was given by the Cambridge University Department of Engineering Ethics Committee. Participants completed seven activities intended to reproduce a range of occupational activity according to the original OSHA protocol 29CFR1910.134 Appendix A, which has since been modified to be shorter [
A range of fit hacks, taken from the internet and from observing the public, were tested with two masks: a KN95 mask and a surgical mask. Fit scores of the mask without a fit hack were compared with the fit scores once the fit hack was applied in order to determine the fit hack’s impact.
In this study, we focus on KN95 and surgical masks as both masks are widely available and, if fit properly, can offer a high degree of filtration. KN95 masks promise similar filtration benefits to N95 masks; however, unlike N95 masks, the public’s access to KN95 masks has been less restricted by this COVID-19 pandemic. While KN95 masks offer significant filtration potential, their poor fit on many individuals negates the potential benefit of these masks [
Seven fit hacks were tested, as shown in
Tape: The edges of the mask are sealed with cloth tape. Care was taken to mould the tape to the face and to seal any gaps between the skin and the edge of the mask.
Stuffed Gaps: First aid gauze was used to fill visible gaps in the mask, until no visible space between skin and mask remained.
Mummy: A roll of first-aid gauze was used to tightly bind the mask to the face, pressing the edges of the mask to the skin of the face.
Pantyhose: Two brands of pantyhose were separately placed over the head to press the mask into place, a method first proposed and tested by Mueller et al. [
Knotting Ear Loops: To make a large mask fit a smaller face, an overhand knot was made of the ear loop elastic near the mask. This hack gained media attention when dentist Dr. Olivia Cui posted a video of herself performing the hack on TikTok [
Rubber Bands: In a hack proposed by Apple engineers, three rubber bands are used to create a ‘brace’ [
The male mannequin head is the size of an average male, while the female represents the size of a small female head or young teen head.
Four participants were tested to determine if the benefits incurred by the application of a fit hack differed significantly between individuals. Participants are identified here by their respective gender and age. Participant F-29 had the smallest head size with a circumference of 54cm. Participants F-51 and F-18 had a circumference of 55cm and 56cm respectively. M-20 had the largest head size, with a circumference of 60cm.
All hacks were tested with two exceptions. These two exceptions were a result of an inability of the wearer to apply the fit hack. In one case, a participant was unable to fit the KN95 mask with ear bands tied, as the adjustment caused the wire of the mask to rub against a painful sore. Another participant was unable to fit pantyhose Brand A over his head as it was too tight and unable to accommodate the participant’s head size. In these two cases, the hack was not tested.
To assess the reliability of these hacks, a further experiment was conducted on one participant. This participant applied each hack five separate times to determine whether changes in fit as a result of the hack were reproducible when the mask is doffed and donned.
Experiments were performed indoors in a clean environment. Temperatures and relative humidity were not precisely measured at the time of experimentation, but are estimated to be between 65 and 75 oF and 65% and 70% respectively. As fit factor is calculated by comparing the relative concentrations of particles inside and outside of the mask, we do not expect this to influence the results. However, it should be noted that particle counts may vary with temperature and humidity.
As shown in
Gray portions of the bars indicate the performance without the application of a fit hack. Green portions of the bars indicate the amount of improvement. The red portion of the bar indicates the amount of decrease in performance.
Pantyhose and cloth tape around the edges of the mask improved fit significantly when applied to surgical masks (see
Gray portions of the bars indicate the performance without the application of a fit hack. Green portions of the bars indicate improvement gained with the application of a fit hack. The red portion of the bar indicates a decrease in performance from applying the fit hack.
The results of a single hack applied multiple times to the same individual were highly consistent in most cases (see
With few exceptions, fit hacks improved the fit factor of both surgical and KN95 masks for all participants. The pantyhose and tape hacks proved to be the most effective hack for both KN95 and surgical masks, with the rubber band hack also showing some promise for surgical masks.
The benefits of each hack differed greatly according to the participant, sometimes in surprising ways. For example, it was expected that fit hacks to make a mask smaller would not significantly benefit participants with large heads. While this proved true for surgical masks, with the individuals with the two smallest heads benefiting the most, it did not hold true for KN95 masks.
An inspection of the fit hacks once applied showed that individual facial features may have a significant impact on fit. For example, a visual inspection of the hacks when applied to participants showed that the nose bridge prevented some hacks from contouring to the sides of the nose, a more significant issue for those with prominent noses (see
This impacted wearers with more prominent noses and provided an example of one facial feature critical to the efficacy of fit hacks.
Discomfort was an issue with many of the hacks. The most discomfort was reported with the pantyhose and the rubber band hacks. The rubber band hack was found to put painful pressure on the ears and face, going so far as to hinder circulation to the ears for some participants. The pantyhose caused high levels of discomfort as well as issues speaking and occasional obstruction of the eyes. The use of tape was reported to be comfortable while worn, but moderate to high levels of discomfort accompanied the tape’s removal. These observations indicate that although a tighter fit provides greater protection, this may be at the expense of the wearer’s comfort.
The most effective fit hack was the use of pantyhose. Placing pantyhose over the mask and head proved an effective way to improve fit, though it should be noted that the brand of pantyhose used was found to have a significant impact on the benefits incurred. We used large sizes of Brand A and Brand B for our experiment. A thigh section was cut to be placed around the head. The material of Brand A was found to be tighter and less flexible. Overall it created an improvement which was, on average, approximately two times greater than that of Brand B. The use of pantyhose generated an improvement for all testers, although one tester was unable to fit the pantyhose over their head. The reliability of the pantyhose when applied multiple times on one tester was variable.
The use of tape to seal the edges of a mask was the second most effective hack. Participants who benefited from the hack the most had an assistant to ensure the tape was correctly placed and no gaps were present. How cloth tape would seal the mask over longer periods of time is unknown as sweat or movement would be expected to degrade the seal of all but the most flexible tape. As expected, the reliability of this hack varied, likely due to how accurately the tape was applied and if the tape became loose in an area at any point during testing.
Higher fit scores were achieved when hacks were applied to the KN95 mask. Although KN95 masks have a high filtration efficiency, the fit is often poor and our results indicate that using KN95 masks with fit hacks can potentially provide high levels of protection. One participant was unable to fit the KN95 mask with ear bands tied. Another participant was unable to fit one brand of pantyhose over his head without the pantyhose tearing. In these two cases, the problematic hack was not tested.
Our findings are consistent with those of Clapp et al (2020), who tested five similar fit hacks, including tying ear loops and applying nylon hosiery over the mask [
Maximizing the protection a mask provides oneself and others rests heavily on improving the fit of the masks. Our results indicate that there is potential for fit hacks to improve the fit of masks, by sealing the edges of the mask or pressing the masks tightly to the face. We would recommend that new mask designs should focus on ensuring that the edges of the mask are firmly in contact with the face.
However, whilst the study does indicate that hacks may be successful, much work remains to be done to create comfortable, effective fit improvements. Many of the most effective fit hacks were so uncomfortable as to be unusable in some cases. Overall, whilst we found that fit hacks did generally improve mask performance, it is difficult to predict the effects for a given individual or face type.
We hope these results will be of benefit to designers in order that they may improve masks and mask fitting devices, as well as members of the public seeking to improve their own masks. The hacks tested are all accessible to the general public. As surgical masks and KN95 masks are commonly worn by healthcare professionals, these findings may assist them improve the protection they are obtaining from their masks. Further research efforts should seek to validate these findings, test a wider variety of fit hacks and expand the range of masks tested to include fabric face coverings.
PONE-D-21-11954
Face Mask Fit Hacks: Improving the Fit of KN95 Masks and Surgical Masks with Fit Alteration Techniques
PLOS ONE
Dear Dr. O'Kelly,
Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.
I received comments and recommendations from two reviewers. Please well address these comments and improve the quality of this manuscript.
Please submit your revised manuscript by Jun 26 2021 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at
Please include the following items when submitting your revised manuscript:
A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'. A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'. An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.
If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.
If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see:
We look forward to receiving your revised manuscript.
Kind regards,
Jianguo Wang, PhD
Academic Editor
PLOS ONE
Journal Requirements:
When submitting your revision, we need you to address these additional requirements.
1. Please ensure that your manuscript meets PLOS ONE's style requirements, including those for file naming. The PLOS ONE style templates can be found at
2. Please provide additional details regarding participant consent. In the ethics statement in the Methods and online submission information, please ensure that you have specified (i) whether consent was informed and (ii) what type you obtained (for instance, written or verbal, and if verbal, how it was documented and witnessed). If your study included minors, state whether you obtained consent from parents or guardians. If the need for consent was waived by the ethics committee, please include this information.
If you are reporting a retrospective study of medical records or archived samples, please ensure that you have discussed whether all data were fully anonymized before you accessed them and/or whether the IRB or ethics committee waived the requirement for informed consent. If patients provided informed written consent to have data from their medical records used in research, please include this information.
[Note: HTML markup is below. Please do not edit.]
Reviewers' comments:
Reviewer's Responses to Questions
1. Is the manuscript technically sound, and do the data support the conclusions?
The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.
Reviewer #1: Yes
Reviewer #2: Yes
**********
2. Has the statistical analysis been performed appropriately and rigorously?
Reviewer #1: Yes
Reviewer #2: Yes
**********
3. Have the authors made all data underlying the findings in their manuscript fully available?
The
Reviewer #1: Yes
Reviewer #2: Yes
**********
4. Is the manuscript presented in an intelligible fashion and written in standard English?
PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.
Reviewer #1: Yes
Reviewer #2: Yes
**********
5. Review Comments to the Author
Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)
Reviewer #1: During the course of the COVID-19 pandemic, there have been suggestions that various techniques could be employed to improve the fit and, therefore, the effectiveness of face masks. It is well recognized that improving fit tends to improve mask effectiveness, but whether these fit modifiers are reliable remains unexplored. This study used quantitative fit testing to assess the fit of both surgical masks and KN95 masks, with and without ‘fit hacks’, on four participants. Seven fit hacks were evaluated to assess impact on fit. Additionally, one participant applied each fit hack multiple times to assess how reliable hacks were when reapplied. The research of this paper is very important and useful. It can be used to effectively improve the fit of surgical and KN95 masks. The detailed comments are presented below:
1. In Fit hacks: All hacks were tested with two exceptions. One participant was unable to fit the KN95 mask with ear bands tied, as the adjustment caused the wire of the mask to rub against a sore. Another participant was unable to fit pantyhose Brand A over his head. In these two cases, the hack was not tested. Can you provide more details?
2. To assess the reliability of these hacks, a further experiment was conducted on one participant. This participant applied each hack five separate times to determine whether the changes in fit from the hack were reproducible when the mask is doffed and donned. The authors say five separate times to determine whether the changes. What's the reference?
3. The high degree of variation between applications of the pantyhose hack may indicate that the hack has the potential to tightly seal the mask to the face, but that this potential is not always achieved during every application. Furthermore, fit factor is not scaled linearly with filtration efficiency, and, within higher fit factor values, small changes in filtration efficiency can be represented as larger changes in fit factor. It is not sufficient to present only the results.
4. The conclusion is too simple, a good conclusion can be a restatement of the central idea, a summary of the research results or main points, some revelatory interpretation or consideration, and a prediction based on the research results? It is recommended to rewrite the conclusion.
Reviewer #2: The manuscript by O’Kelly and colleagues entitled “Face Mask Fit Hacks: Improving the Fit of KN95 Masks and Surgical Masks with Fit Alteration Techniques” aims to assess whether the common “fit hacks” improve the surgical and KN95 mask performance. The notion of improving facemask performance is still an important interventional strategy to reduce SARS-COV-2 transmission as parts of the world are still experiencing serious outbreaks and vaccination campaign still requires time to inoculate naïve populations. I believe this manuscript proves important information of improving mask efficiency and should be published. However, major revision is necessary to answer some questions.
1) Please note there is a difference between a surgical mask (tie) and a procedural mask (earloop). I believe the ones tested in this manuscript are procedural masks.
2) Please indicate the models and manufacturers of the masks tested.
3) The abstract could be more concise, especially the “Results and Discussion” section. I also recommend not using vague words, such as “most” and “many”, repeatedly. How many fit hacks are effective exactly?
4) Line 65. The claim is not accurate because there are other reasons driving the necessity to wear a “surgical” mask or a KN95 in the public. For example, one would prefer a “surgical” mask than N95 because of comfort? In addition, please explain why not testing cloth masks. They are also widely available to and used by the public.
5) Line 67. Besides fit, material type is also important in filtration efficiency.
6) The authors have talked a lot about the “fit” of mask and explained what the fit is at line 75. I would suggest expanding the explanation and mentioning it earlier so that it will help readers to understand.
7) Line 94-97. I think emphasizing the advantage of quantitative over qualitative fit testing here is not necessary. If the authors really think these are necessary, I believe they should belong to the discussion section.
8) Line 100. What exactly is the standard formula? I think providing the formula or equation will really help readers understand how the quantitative method works, including how the fit factor scores were assigned.
9) Line 106: does a Portacount generate real time data output, or just a summary of the whole test results? Is it only giving a “pass” or “fail” result?
10) Line 110: have the researchers monitored the relative humidity and temperature of the testing environment? I think reporting these data are important since the relative humidity seems to affect the particle count significantly.
11) Line 115: The test protocol involves breathing, talking, bending over, and turning the head. Which exact protocol in 29 CFR § 1910.134 was used? Table A-1, A-2, or A-3?
12) The data based on fit factor score is hard to understand without knowing how it was calculated and without a good comparing taget. For example, it will help if a N95 with good fit is tested (assuming >=95% particles were blocked from entry into the mask) and assigned a score.
13) Another common hack that could improve the mask performance is using a hook to tie the two earloops behind the head. Have you considered and tested this?
14) Line 274. I thought this paper was mainly to improve mask performance of the masks available and worn by the public. Healthcare workers seem to have no N95 shortage now, at least in the US.
**********
6. PLOS authors have the option to publish the peer review history of their article (
If you choose “no”, your identity will remain anonymous but your review may still be made public.
Reviewer #1: No
Reviewer #2: No
[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.]
While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool,
Reviewer #1: During the course of the COVID-19 pandemic, there have been suggestions that various techniques could be employed to improve the fit and, therefore, the effectiveness of face masks. It is well recognized that improving fit tends to improve mask effectiveness, but whether these fit modifiers are reliable remains unexplored. This study used quantitative fit testing to assess the fit of both surgical masks and KN95 masks, with and without ‘fit hacks’, on four participants. Seven fit hacks were evaluated to assess impact on fit. Additionally, one participant applied each fit hack multiple times to assess how reliable hacks were when reapplied. The research of this paper is very important and useful. It can be used to effectively improve the fit of surgical and KN95 masks. The detailed comments are presented below:
1. In Fit hacks: All hacks were tested with two exceptions. One participant was unable to fit the KN95 mask with ear bands tied, as the adjustment caused the wire of the mask to rub against a sore. Another participant was unable to fit pantyhose Brand A over his head. In these two cases, the hack was not tested. Can you provide more details?
In one case the participant had a large and painful acne cyst at the time of testing. Tying the ear bands of the KN95 both adjusted the line of the mask and caused the mask to press tighter so that the edge of the mask was pressing against the cyst. The participant reported the hack was painful and it was thus discontinued.
For the pantyhose test, an approximately 10” section of pantyhose was taken from the thigh of the pantyhose. The pantyhose cross section is an elastic circle. One participant could not fit the pantyhose over their head as the material did not have enough ‘give’ or ‘stretch’.
Some extra detail has been added to the manuscript, however we don’t think that there is much value in providing copious detail.
2. To assess the reliability of these hacks, a further experiment was conducted on one participant. This participant applied each hack five separate times to determine whether the changes in fit from the hack were reproducible when the mask is doffed and donned. The authors say five separate times to determine whether the changes. What's the reference?
This has been edited. We hope this sentence is clearer now.
3. The high degree of variation between applications of the pantyhose hack may indicate that the hack has the potential to tightly seal the mask to the face, but that this potential is not always achieved during every application. Furthermore, fit factor is not scaled linearly with filtration efficiency, and, within higher fit factor values, small changes in filtration efficiency can be represented as larger changes in fit factor. It is not sufficient to present only the results.
Each time the pantyhose was applied; it would compress the mask to the face. However, getting pantyhose over the head was difficult. Sometimes the process of putting it on would disturb the mask’s placement, so that in some cases the mask could become tilted or moved off center. Another thing which influenced fit was hair style. Just putting a ponytail higher or lower could change how tight the pantyhose pressed the mask to the face. We have added this to the manuscript.
4. The conclusion is too simple, a good conclusion can be a restatement of the central idea, a summary of the research results or main points, some revelatory interpretation or consideration, and a prediction based on the research results? It is recommended to rewrite the conclusion.
The conclusion has been rewritten.
Reviewer #2: The manuscript by O’Kelly and colleagues entitled “Face Mask Fit Hacks: Improving the Fit of KN95 Masks and Surgical Masks with Fit Alteration Techniques” aims to assess whether the common “fit hacks” improve the surgical and KN95 mask performance. The notion of improving facemask performance is still an important interventional strategy to reduce SARS-COV-2 transmission as parts of the world are still experiencing serious outbreaks and vaccination campaign still requires time to inoculate naïve populations. I believe this manuscript proves important information of improving mask efficiency and should be published. However, major revision is necessary to answer some questions.
1) Please note there is a difference between a surgical mask (tie) and a procedural mask (earloop). I believe the ones tested in this manuscript are procedural masks.
My understanding is that the term surgical mask is an overarching definition which includes masks which can be secured by tie or earloop. We have now specified that the masks had earloops and added the term ‘procedural masks’.
2) Please indicate the models and manufacturers of the masks tested.
This has been added.
3) The abstract could be more concise, especially the “Results and Discussion” section. I also recommend not using vague words, such as “most” and “many”, repeatedly. How many fit hacks are effective exactly?
The abstract has been edited to make it more specific.
4) Line 65. The claim is not accurate because there are other reasons driving the necessity to wear a “surgical” mask or a KN95 in the public. For example, one would prefer a “surgical” mask than N95 because of comfort? In addition, please explain why not testing cloth masks. They are also widely available to and used by the public.
Each cloth mask has its own shape and there is considerable heterogeneity in the style of these masks. It would be hard to create generalizable findings. In a separate study, we have assessed the performance of home-made fabric face masks.
5) Line 67. Besides fit, material type is also important in filtration efficiency.
This has been noted.
6) The authors have talked a lot about the “fit” of mask and explained what the fit is at line 75. I would suggest expanding the explanation and mentioning it earlier so that it will help readers to understand.
This discussion has been expanded.
7) Line 94-97. I think emphasizing the advantage of quantitative over qualitative fit testing here is not necessary. If the authors really think these are necessary, I believe they should belong to the discussion section.
We do think that highlighting the importance of quantitative fit testing in the methodology over qualitative testing is important as it clarifies to readers that we are not using qualitative methods that they might have encountered when fit testing masks in hospitals. Healthcare facilities often use qualitative fit testing, which relies on users saying whether or not they can taste a test solution which is sprayed around the mask. Since we expect that the article will be of interest to healthcare workers, we wish to clarify that this method (which they may be familiar with) was not the method used.
8) Line 100. What exactly is the standard formula? I think providing the formula or equation will really help readers understand how the quantitative method works, including how the fit factor scores were assigned.
The formula has been added.
9) Line 106: does a Portacount generate real time data output, or just a summary of the whole test results? Is it only giving a “pass” or “fail” result?
Real time data is available and then a summary is provided with the quantitative fit factor. The pass/fail result is based on the quantitative result.
10) Line 110: have the researchers monitored the relative humidity and temperature of the testing environment? I think reporting these data are important since the relative humidity seems to affect the particle count significantly.
Temps were between 65* and 75* F and humidity was between 65% and 70%. We have not included these data in the manuscript as they were not precisely measured at the time of the study. However, article density is taken into consideration by the machine formula. Fit factor is calculated by comparing ambient particles and particles in the mask – it is percentage.
11) Line 115: The test protocol involves breathing, talking, bending over, and turning the head. Which exact protocol in 29 CFR § 1910.134 was used? Table A-1, A-2, or A-3?
Table A-2
12) The data based on fit factor score is hard to understand without knowing how it was calculated and without a good comparing taget. For example, it will help if a N95 with good fit is tested (assuming >=95% particles were blocked from entry into the mask) and assigned a score.
Please note that this information is present in the manuscript: “When the fit of N95 or FFP3 masks are assessed, a score of at least 100 is required for the mask to be considered to have adequate fit”
13) Another common hack that could improve the mask performance is using a hook to tie the two earloops behind the head. Have you considered and tested this?
We are aware of this hack and use it ourselves in the research group… however, we have unfortunately not yet tested this. Our understanding is that the main purpose hack is used to improve comfort rather than the fit of the mask.
14) Line 274. I thought this paper was mainly to improve mask performance of the masks available and worn by the public. Healthcare workers seem to have no N95 shortage now, at least in the US.
This paper is mainly to help the public, although there is applicability for healthcare workers. Surgical masks and KN95 masks are commonplace in hospitals around the world, with KN95s being prominently used by Asian healthcare workers.
Submitted filename:
PONE-D-21-11954R1
Face Mask Fit Hacks: Improving the Fit of KN95 Masks and Surgical Masks with Fit Alteration Techniques
PLOS ONE
Dear Dr. O'Kelly,
Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.
==============================
ACADEMIC EDITOR:
Further revision is necessary. Please address the comments from one reviewer.
==============================
Please submit your revised manuscript by Nov 08 2021 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at
Please include the following items when submitting your revised manuscript:
A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'. A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'. An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.
If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.
If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see:
We look forward to receiving your revised manuscript.
Kind regards,
Jianguo Wang, PhD
Academic Editor
PLOS ONE
[Note: HTML markup is below. Please do not edit.]
Reviewers' comments:
Reviewer's Responses to Questions
1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.
Reviewer #1: All comments have been addressed
Reviewer #2: (No Response)
**********
2. Is the manuscript technically sound, and do the data support the conclusions?
The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.
Reviewer #1: Yes
Reviewer #2: Partly
**********
3. Has the statistical analysis been performed appropriately and rigorously?
Reviewer #1: Yes
Reviewer #2: Yes
**********
4. Have the authors made all data underlying the findings in their manuscript fully available?
The
Reviewer #1: Yes
Reviewer #2: Yes
**********
5. Is the manuscript presented in an intelligible fashion and written in standard English?
PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.
Reviewer #1: Yes
Reviewer #2: Yes
**********
6. Review Comments to the Author
Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)
Reviewer #1: The revisions are satisfactory to this reviewer. The manuscript is recommended for publication in its current form.
Reviewer #2: Please see the attachment. Please see the attachment. Please see the attachment. Please see the attachment.
**********
7. PLOS authors have the option to publish the peer review history of their article (
If you choose “no”, your identity will remain anonymous but your review may still be made public.
Reviewer #1: No
Reviewer #2: No
[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.]
While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool,
Submitted filename:
We would like to once again thank the reviewers for their thoughtful comments. We have revised the work in response to these, and a letter detailing our changes in response to each comment can be found in this submission.
Submitted filename:
Face Mask Fit Hacks: Improving the Fit of KN95 Masks and Surgical Masks with Fit Alteration Techniques
PONE-D-21-11954R2
Dear Dr. O'Kelly,
We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.
Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.
An invoice for payment will follow shortly after the formal acceptance. To ensure an efficient process, please log into Editorial Manager at
If your institution or institutions have a press office, please notify them about your upcoming paper to help maximize its impact. If they’ll be preparing press materials, please inform our press team as soon as possible -- no later than 48 hours after receiving the formal acceptance. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact
Kind regards,
Jianguo Wang, PhD
Academic Editor
PLOS ONE
Additional Editor Comments (optional):
Reviewers' comments:
Reviewer's Responses to Questions
1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.
Reviewer #1: All comments have been addressed
Reviewer #2: All comments have been addressed
**********
2. Is the manuscript technically sound, and do the data support the conclusions?
The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.
Reviewer #1: Yes
Reviewer #2: Yes
**********
3. Has the statistical analysis been performed appropriately and rigorously?
Reviewer #1: Yes
Reviewer #2: Yes
**********
4. Have the authors made all data underlying the findings in their manuscript fully available?
The
Reviewer #1: Yes
Reviewer #2: Yes
**********
5. Is the manuscript presented in an intelligible fashion and written in standard English?
PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.
Reviewer #1: Yes
Reviewer #2: Yes
**********
6. Review Comments to the Author
Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)
Reviewer #1: The revisions are satisfactory to this reviewer. The manuscript is recommended for publication in its current form.
Reviewer #2: The authors have addressed all my comments. This is a great study that will offer impactful information to improve mask performance for the public during the pandemic.
**********
7. PLOS authors have the option to publish the peer review history of their article (
If you choose “no”, your identity will remain anonymous but your review may still be made public.
Reviewer #1: No
Reviewer #2: No
PONE-D-21-11954R2
Face Mask Fit Hacks: Improving the Fit of KN95 Masks and Surgical Masks with Fit Alteration Techniques
Dear Dr. O'Kelly:
I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now with our production department.
If your institution or institutions have a press office, please let them know about your upcoming paper now to help maximize its impact. If they'll be preparing press materials, please inform our press team within the next 48 hours. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information please contact
If we can help with anything else, please email us at
Thank you for submitting your work to PLOS ONE and supporting open access.
Kind regards,
PLOS ONE Editorial Office Staff
on behalf of
Dr. Jianguo Wang
Academic Editor
PLOS ONE