The design of the facegaiter centers on source control, with the added benefit of effective wearer protection. Dr. Paul Baglin, owner of tensARC Ltd saw a need for a source control approach when the COVID-19 pandemic began. Working from prior training and intensive experimentation he and his research team validated the facegaiter design and its special construction from common “low-tech” synthetic materials.
Improving face coverings for use by the public is a wide-ranging topic that draws from multiple areas of expertise. Our research effort had helpful guideposts from diverse research teams seeking to understand and reduce risks from bioaerosols. We learned from journal articles, workshop presentations, interviews, and other forms of outreach to which such experts devoted their time and attention – especially during the pandemic – so that others could benefit from their knowledge.
The facegaiter version we arrived at is the MK3 (“mark three”) version. Our research, knowledge development and support to standardisation organisations, however, will continue.
Identifying the problem with current mask types
When you – and everyone else – breathes, talks, coughs, or sneezes, the air that is exhaled contains thousands of droplets and aerosols made mostly of water but also containing little bits of other organic material. If a person is infected with a virus then these bits may contain active “copies” of the virus. How many copies precisely is a big question and cannot be determined outside of a laboratory, and also will vary considerably from person to person.
An active virus that’s exhaled can become airborne and one person can directly infect another in this way. Masks and other face coverings can work to reduce the transfer of active virus, both outwardly, from the infected wearer to the environment (called source control) and inwardly, from the environment to the wearer (called wearer protection).
Blocking what’s breathed out at the source is the more effective way to reduce infection rates. There’s a gap in source control mask research, though, probably because it is harder to ask people to wear a mask for source control.
Creating a source control solution
The gap in research described above reflects a classic “market failure” – a need that has gone unmet because there’s been no driver for private investment in resolving it.
The pandemic became a driver when the government, the media, and public health officials began to form and communicate a response. We did our own initial research and mapped out some options. We utilized almost two decades in fabric design, engineering and manufacture to design a new type of face covering, but we knew other forms of expertise would be needed. Very fortunately, the UK and Scottish governments were seeking to fund new innovation to help address the COVID-19 pandemic.
Here’s how we came up with our research plan to confirm a new, “source control” approach and support our efforts to bring an effective face covering to market.
We knew that respirators (FFP2, N95, etc.) – largely worn by healthcare workers – have a tight seal around the nose and mouth, which is sufficient but only when the respirators are fitted well. Seals reduce leakage, both inward (from the environment, other people) and outward (from the wearer).
We noticed that surgical masks – and the cloth masks used in place of respirators and surgical masks by the public – have gaps at the sides, nose and under the chin. The wide variety of mask types and facial types means these gaps can be minor or major. In either case, they produce leaks that reduce the protection provided by the mask.
In addition to seals, the fabric choice can affect a mask’s ability to filter pathogens and other materials. We looked at multiple studies testing many fabric types, including those comparing the materials used for cloth masks, respirators and surgical masks. Finally, depending on the seal and fabric types, breathing – as well as talking, singing, coughing, sneezing, and other exhalation – puts pressure on the inside of the mask, increasing the size of existing gaps and leaks. With more force, e.g. louder talking, there can be an increase in aerosols and an increase in pressure on the mask, so, a larger risk of leakage from gaps which is compounded by low porosity fabric construction.
Addressing the leaks from pressure led us to re-think the design of the masks being used for public health purposes during the COVID-19 pandemic.
As a result, we confirmed the design of a face covering built around source-control as the primary objective.
We made the observations and design decisions above during the initial design effort.
Soon after, we added experts in physiology, microbiology, and infection control from the University of the West of Scotland. Our team pursued a research plan with several parts:
1. We continued to develop the unique face gaiter design and manufactured several versions.
2. We tested fabrics for their potential to block aerosols.
3. We took the most promising fabrics and made them into facegaiters. We tested these for how well they can block what a wearer may exhale, compared to surgical masks, other cloth masks, and FFP2/N95 masks. This helped validate our source control design.
4. We tested for comfort. Ten subjects wore the facegaiter at rest and at light and moderate exercise, each for 30 minutes. Our research found the face gaiter had no negative impacts as to blood oxygen levels, carbon dioxide build up in the mask, and other physiological indicators of wearer fatigue.
5. We tested these face coverings using two mechanical mannequins: one as the “source” of the infection and one as “susceptible” to being infected by the source. This approach tested source control, user protection and the enhanced benefit when both wear a mask.
Throughout the testing, we validated specific design parameters for the facegaiter.
Developing design parameters and requirements: details on the facegaiter “source-control” design
A) Specifically designed to reduce leakage. The first design requirement for facegaiter was to reduce leakage and thereby improve source control performance. We rethought the surgical mask: many manufacturers use the surgical mask “half face” style as the model for the cloth masks they sell for non-medical purposes, but many studies document leakage as an issue for study. So, we studied this.
We moved the seals at the edge of the mask farther away from the complex shape around your nose and mouth which varies from person to person and moves when you talk. In place of the seal types and locations used on other masks, we used simple seals: a top seal around the head, under the eyes and across the nose: and a bottom seal by draping the fabric across your shoulders.
B) Filter efficiency. A second design requirement was a fit-for-purpose filter, to specifically address source control. The entire front panel is a filter, because the same design that stops leakage – an elongated “gaiter” style – permits us to put in a much larger filter (at least 6x larger than other masks). A larger filter reduces air resistance making it easier to breathe and it also reduces the airspeed through the filter. The lower air speed increases filter performance so the same filter can stop more aerosols and work for longer.
- The face gaiter has multiple layers of different fabrics tested for optimal filtration.
- A seal at the bottom is designed to help the filter fabric contain exhaled air.
- Another seal at the top blocks air flowing up from the nose and mouth towards the eyes, a common leakage site. This nose seal also reduces fogging in a wearer’s glasses and dry eye issues.
C) Safety and comfort. A third requirement was safety and comfort. The low air speed and lower pressure within the mask during use makes it easier for you to wear. Facegaiter has passed key physiological tests. Comfort for the wearer helps normalise face coverings and helps us comply for longer stretches of time during the day. There’s no fussing or adjusting gaps or straps. The supple fabric enhances the seal and also feels better against the skin. We use sizing to improve comfort and performance – only a single measurement is needed.
D) Practicality. A fourth requirement was practicality, covering user acceptance, scalability, and sustainability. We surveyed users for their response to the facegaiter. Their inputs helped with look and feel especially; and we sourced fabrics with beautiful colours and classic patterns. We considered the evolution of masking policy, its place among other public health interventions, as well as possible needs under future disease outbreaks, epidemics or pandemics. We sought quality, UK-made fabrics to ensure a robust and transparent supply chain, and leveraged our ability to repurpose fabric stocks.
E) Reusable face covering. A fifth set of requirements was convenience, washability, and durability. Based on our testing, we could select fabrics that don’t degrade quickly and can withstand many washes. Plus, because the facegaiter design means the filter doesn’t have to work as hard, we can get the same mask performance from a more durable filter material. The materials we tested and selected can be washed many times without degrading. The facegaiter can be washed, tumble dried, and reused more than 100 times.
F) Protection. Last, but by no means least is the requirement to also provide protection to the wearer. Although the facegaiter is designed for source control, we tested it for wearer protection.
We have tested the face gaiter for several key factors.
- Essential safety.
- We looked at how much carbon dioxide may build up when a person wears an FFP2 or a face gaiter, both at rest and when exercising. We examined what happens under light and moderate exercise. Taken together, these reflect activities in occupations that do not require heavy labor.
- The physiology team found that the facegaiter performed very well and similar to an FFP2/N95 respirator but with a lower thermal sensation (doesn’t feel as hot when you wear it)
Balancing filtration, air pressure, and leakage
- Viruses and other pathogens in the respiratory system may leave the body when breathing, coughing, etc., as part of an aerosol
- Aerosols are fine particles or liquid suspended in air, very often invisible to the eye. Those over 10 microns may fall by their weight to the ground, while smaller sizes can remain in the air for long periods of time.
- Some viruses are transmitted not only by droplets when you talk or cough, but the smaller aerosols carrying the virus that stay airborne. A better mask can contain more of the bioaerosols which transmit pathogens.
- Assuming that very fine aerosols may need to be controlled, we studied fabrics and various face gaiter designs to optimise performance.
- Before testing the face gaiter with an actual pathogen, we generated fine aerosols from a solution similar to saliva and tested a set of fabrics for the following:
- Filtration efficiency: filtration of what may be inhaled by the wearer
- Source control: filtration of what a wearer exhales into the environment
- Containment of bacteria and virus
- We also tested fabrics for their ability to filter bacteria and virus.
- We have performed preliminary tests by the Polymerase Chain Reaction (PCR) method using an animal coronavirus (SARS-CoV2 surrogate). So far, preliminary data show a 90% reduction in virus detection in air passed through the fabric. Tests will continue so to understand the effectiveness against pathogens.
- Managing pressure on the filter and the rest of the mask
- An effective filter will block the virus but at the same time, it may also restrict the air from passing through it, the pressure created increases leakage and makes it harder for the wearer to breathe.
- We tested the filtration ability of the filter fabrics on their own and the complete facegaiter. In this way we were able to determine the impact of the facegaiter design on filtration.
- As expected from our understanding of filtration materials and the results of other researchers’ studies, dense fabrics block larger droplets well. In contrast to droplets, however, smaller aerosols take advantage of leaks. Leaks out of the sides of a half-face mask worn by an infected person, for example, could contain the virus. These aerosols that escape with the leaking air may remain airborne and pose a risk to others in the same room.
- Even the best FFP2/N95 and FFP3/N99 masks can also leak, especially when exhaling and if used multiple times.
- Even a small leak makes a big difference.
- Our tests and other researchers’ studies indicate that most cloth masks also leak in a way that substantially drops their performance.
- If you are wearing a surgical mask you have a high-performance filter capable of stopping around 95% of aerosols. However, just one tiny gap at the bridge of the nose could allow 50% of the aerosols to bypass the filter, dropping performance to less than 50%.
- Visible gaps at the sides of the surgical mask can indicate that 80% or more of the aerosols may bypass the filter; at that point the performance of the mask may be less than 20%.
- Prior studies and our tests demonstrated these masks leak. So, we had to address it.
Acceptability to users
- We surveyed a set of people who were given a free facegaiter and, at the end of two weeks, surveyed for their opinions on comfort, ease of use, and frequency of use.
- These subjects were not associated with the research team and were selected and tested pursuant to a university Ethics programme.
- A majority of the users stated that the facegaiter remains cooler under exercise than an FFP2/N95. Also, the subjects experienced no significant difference in blood oxygen levels or in carbon dioxide inside the mask.
- The materials we tested and selected can be washed many times without degrading. The facegaiter can be washed, tumble dried, and reused more than 100 times with no reduction in fit or performance. Testing continues……..
Conducting additional R&D
We are continuing to support our university partners and will support others seeking to work in this area of research.