Owlstone Medical Publishes Data on the Use of Face Mask Filters to Capture Viral Particles for SARS-CoV-2 Detection

Published on: 20 Jul 2021, under COVID-19

  • Study published in Nature Scientific Reports demonstrates embedded filters capture virus particles with limits of detection of ~10 copies per filter
  • Data consistent with findings that COVID is most infectious in early disease where breath aerosol viral load is highest
  • Sample collection by mask filter has strong potential applications in detection of bacterial and fungal respiratory infections

Cambridge, UK, 20 July 2021: Owlstone Medical (or the “Company”), the global leader in Breath Biopsy® for applications in early disease detection and precision medicine, today announced the publication of a peer-reviewed study in Nature Scientific Reports1. The paper investigates the performance of filters embedded in face masks for supporting the detection of SARS-CoV-2, as an alternative to nasopharyngeal swabs (NPS).  

Diagnostic testing has been a cornerstone of the fight against COVID-19 from the start of the pandemic, however NPS, the gold standard for collection of samples, can be uncomfortable and difficult to administer. Therefore, a system that could passively collect a sample as part of daily routine would be of significant advantage as testing continues to be necessary in disease monitoring and control.

It is well understood that exhaled respiratory droplets or aerosols are the most common route of transmission of COVID-19, and that face masks are highly effective at limiting spread. This suggests that face masks retain viral particles and therefore could provide a convenient and non-invasive method of sampling for subsequent diagnostic testing.

To explore this, Owlstone Medical applied its breath-based diagnostic research expertise and Breath Biopsy technology to develop a system for the controlled generation of small aerosol particles to measure the limit of detection of viral capture on filters. Following this, hospitalized patients with confirmed COVID-19 were recruited to give samples of exhaled breath aerosol by breathing into a face mask for comparison with samples collected with NPS.

Study results demonstrated the ability of embedded filters to capture virus particles with very good limits of detection (~10 copies per filter). However, the study went on to show that viral load in COVID-positive patients had a significant impact on concordance between sample collection approaches, with the sensitivity of SARS-CoV-2 detection when using samples extracted from filters at less than 10% of NPS, with the positive cases correlating in those with the highest viral loads. These results are consistent with other studies where approximately 10% patients can account for as much 80% of infections2 and in later stages of disease, patients stay swab positive despite being non-infectious.

An additional consideration is that SARS-CoV-2 differs from many other respiratory viruses in that viral load in exhaled breath aerosols and infectiousness is highest before symptom onset and decreases thereafter3,4. As the majority of patients enrolled in the Company’s study had been first diagnosed and admitted to hospital several days before the collection of samples, this was proposed as a significant contributor to study findings.  

These findings are in line with other recently published studies5,6, and suggest that a mask filter approach could potentially differentiate patients in the early stage of disease when they are most infectious. Further, there is strong evidence for mask-based sampling for the detection of bacteria or fungi such as Mycobacterium tuberculosis7, Aspergillus species8, or Pseudomonas aeruginosa9.

Billy Boyle, co-founder and CEO at Owlstone Medical said: “While our study demonstrated that the detection of SARS-CoV-2 on mask filters may not be suitable except for early disease, we are encouraged that our findings mirror that of the wider literature. More importantly, we now have a powerful capability to sample and analyze exhaled breath aerosol that can be more broadly applied. The potential to use mask filters to diagnose tuberculosis and other bacterial infections, and the ability to do so non-invasively, holds tremendous promise for community-based testing.”

Read the full paper

We have also discussed the results of this study in a new research case study.




Notes to Editors:

For more information please contact:

Sarah Jeffery, Zyme Communications
+44 (0) 7771-730919


Frazer Hall, MEDiSTRAVA Consulting

+44 (0) 20 7638 9571



  1. Smolinska, A., et al., The SARS-CoV-2 viral load in COVID-19 patients is lower on face mask filters than on nasopharyngeal swabs. Sci Rep, 2021. 11(1): p. 13476. DOI: 10.1038/s41598-021-92665-3
  2. Why do some COVID-19 patients infect many others, whereas most don’t spread the virus at all? https://www.sciencemag.org/news/2020/05/why-do-some-covid-19-patients-infect-many-others-whereas-most-don-t-spread-virus-all
  3. Benefield, Amy E., et al., SARS-CoV-2 viral load peaks prior to symptom onset: a systematic review and individual-pooled analysis of coronavirus viral load from 66 studies. 2020. https://www.medrxiv.org/content/10.1101/2020.09.28.20202028v1  
  4. He, Xi., et al., Temporal dynamics in viral shedding and transmissibility of COVID-19. Nature Medicine, 2020. 26, 672–675. DOI: 10.1038/s41591-020-0869-5
  5. Williams, Caroline M., et al., Exhaled SARS-CoV-2 quantified by face-mask sampling in hospitalised patients with COVID-19. Journal of Infection, 2021. 82, 6, 253-259. DOI: 10.1016/j.jinf.2021.03.018
  6. Sriraman, Kalpana., et al., Non-Invasive Sampling Using an Adapted N-95 Mask: An Alternative Method to Quantify SARS-CoV-2 in Expelled Respiratory Samples and Its Implications in Transmission. 2020. DOI: 10.2139/ssrn.3725611
  7. Williams, Caroline M., et al., Exhaled Mycobacterium tuberculosis output and detection of subclinical disease by face-mask sampling: prospective observational studies. Lancet Infect Dis 2020. 20, 607–17. DOI: 10.1016/S1473-3099(19)30707-8
  8. Maschmeyer, G., et al., A prospective, randomised study on the use of well-fitting masks for prevention of invasive aspergillosis in high-risk patient. Ann Oncol, 2009. 20, 9, 1560-1564. DOI: 10.1093/annonc/mdp034
  9. Vanden Driessche, Koen., et al., Surgical Masks Reduce Airborne Spread of Pseudomonas aeruginosa in Colonized Patients with Cystic Fibrosis. American Journal of Respiratory and Critical Care Medicine, 2015. 192, 7, 897-899. DOI: 10.1164/rccm.201503-0481LE


What is Breath Biopsy®?

Breath Biopsy represents an entirely new and non-invasive way to address two of the major challenges of healthcare today: early detection of disease and precision medicine.

Breath Biopsy generates valuable disease insights by determining the chemical makeup of breath through the measurement of volatile organic compounds (VOCs), gaseous molecules that can be sampled quickly and non-invasively.

VOCs originate from all parts of the body as the end product of metabolic processes, making Breath Biopsy applicable to a wide range of diseases including cancer, liver disease, and respiratory disease. Breath also contains microscopic aerosol particles from the lungs and airways, which can contain a wide range of biomarkers including for infectious disease.

Breath collection is carried out using Owlstone Medical’s ReCIVA® Breath Sampler, which ensures reliable, reproducible collection of VOCs. Samples of exhaled breath are captured and stabilized on Breath Biopsy Cartridges, which can then be shipped to Owlstone Medical’s Breath Biopsy lab for analysis, using Thermo Fisher Scientific Orbitrap™ Mass Spectrometry or FAIMS to determine their VOC profile. Advanced data analytic techniques can then be applied in order to pinpoint the VOCs of interest.


About Owlstone Medical (www.owlstonemedical.com):

Owlstone Medical’s vision is to save 100,000 lives by realizing the enormous promise of breath-based diagnostics through the development and application of Breath Biopsy®.

Owlstone Medical’s world-leading Breath Biopsy platform includes ReCIVA®, a proprietary sample collection device that can take stable breath samples anywhere, the world’s only commercial Breath Biopsy Laboratory located in Cambridge, U.K. with support through our office in Research Triangle Park, NC, USA, and the development of the world’s largest Digital Breath Biobank matched to patient phenotype.

Owlstone Medical is deploying the platform to address some of the key challenges of 21st century healthcare. The focus is on the development of Tests and RUO Panels for the early detection of disease with an emphasis on cancer, and on precision medicine initially targeting liver and respiratory disease.

The Breath Biopsy OMNI (Owlstone Medical Novel Insights) Assay is Owlstone Medical’s comprehensive solution for end-to-end breath sample collection and VOC analysis, which is being deployed with large pharma including AstraZeneca, Actelion Pharmaceuticals (a J&J company), and GlaxoSmithKline, and leading academic institutions. Owlstone Medical’s technology is currently in use at over 100 sites worldwide.

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Breath Biopsy® OMNI: advanced global breath VOC analysis

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