Today, the world is much more familiar with masks and masking than before the pandemic.

Reusable fabric masks must address many physical and human factors in their design, fabrication, and use. A solution should avoid physiological and health impacts from wearing and reuse, while filtration, breathability, fit, seal, and comfort must meet desired performance levels.

tensARC formed a team of experts in engineering, textile science, physiology, microbiology, infection control and public health. We used a mechanistic approach to design and develop a new solution from the ground up. Prototypes and benchmarks (e.g., FFP2/N95 respirators) were tested in house with a specially developed, artificial breathing device having two (“source” and “susceptible”) manikins. A knowledge base on face covering design and use was assembled and used at each stage of research, development, manufacture, and commercialisation.

The resulting solution, facegaiter, is effective and can be worn comfortably by people with facial hair, hearing aids and glasses. Our solution meets social and environmental sustainability aims, being recyclable, having a universal fit for all face shapes, and being reusable hundreds of times with high performance.

Minimising leakage by design

From the start, guiding principles were controlling transmission of respiratory hazards at the source (“source control”) and convenience, to make it easy to comply with masking policies. The pandemic emergency was occurring, and respiratory transmission of the virus was a primary concern in designing the mask. Later, we saw its broader applications.

Our research focused on leakage. Leaks occur from gaps or when the seal along the skin is broken, as shown by this photo of medical mask leaks. A tubular shape locates seals away from the jaw and jaw movements (e.g., talking), reducing the risk of mask slippage and seal failure during use.

In addition to selecting a tubular shape, we chose fabrics with the right properties to structure an internal space for air flow, called a plenum. A tubular shape also permits use of an oversize filter. The embedded, oversize filter and plenum mechanism were optimized to enhance filter performance during normal respiratory activities (light and heavy breathing). During high velocity events, e.g., coughing and sneezing, this design reduces the risk of seal failure and leaks. A foam nose seal was added to minimise leaks, since it can deform and seal across the nose bridge of each individual face.

A single measurement around the head determines the wearer’s size. After that simple sizing exercise at home, each wearer gets a consistent level of fit. An adjustable strap is in the back to enhance comfort.

Developing a suitable filter

We developed two options for the filter assembly, which forms the whole front section of the facegaiter.  Both alternatives  have three layers, filter at a high level, minimise leakage and address other key considerations.   Both filter options make the facegaiter more breathable than a respirator.   

Filter A provides extremely low air flow resistance and is highly durable, retaining high performance after hundreds of washes.  Filter B is also highly durable and more breathable than a respirator but slightly less breathable than Filter A. Filter B's filtration performance is higher than Filter A's for the very smallest particles, and is similar to an FFP2/N95 respirator. 

A suitable filter needs to do more than capture the particles of concern.  Additional considerations for mask filters include: 

  • Ensuring that air flows easily through the filter to make the face covering easier to wear and to reduce the pressure on the seals. 
  • Optimising the inner fabric to minimise skin abrasion and to enable wicking which prevents moisture accumulation.  
  • Choosing suitable textiles so that the filter fabric and the fabric for the entire face covering permit extended storage before and during periods of use. 
  • Creating fabric assemblies that can be laundered at home to make them easy to decontaminate and be ready for safe reuse. 

Assessing performance to lab standards and as worn

We tested facegaiter prototypes against common measures of mask effectiveness, e.g., breathability and filter performance.  They compared well to benchmark solutions, but there were other aspects to measure.   

The facegaiter was conceived as an integrated solution whose whole would be better than the sum of its parts: specifically, the tubular shape also used a plenum (formed by unique stitching) working with an oversized three-layer filter to manage air flows, and there were engineered seals to minimise gaps and leaks.  Therefore, we also assessed performance “as a whole” and “as worn”.  

To test “whole mask” performance, as worn, a facegaiter (with Filter A), a respirator (N95/FFP2), and medical face mask were tested for wearer protection on a breathing manikin placed within a 400-liter test chamber. The setup was run with two challenge aerosols: 12% NaCl dried particles (not discharged to Boltzman equilibrium) and DEHS liquid particles (zero charge).  The breathing rate was 30L/min tidal (mild exercise) with a peak flow of approximately 94L/min. Masks were first tested ‘naturally fitted’ to determine Total Inward Leakage then re-tested with the edges taped to prevent all edge leakage and measure filter performance alone.  

Results suggested effectiveness similar to that of a respirator.  These test results are summarised in our May 2022 poster presentation at the biennial conference of the International Society for Respiratory Protection (ISRP).   

Summary of Independent testing & partnerships

4Ward (UK) - Filtration BS EN 14683 Medical face masks

facegaiter (filter A)
after 100 wash cycles
Sample 1 (off seam)Sample 2 (off seam)Sample 3 (off seam)Sample 4 (off seam)Sample 5 (off seam)Threshold (EN14683)Result
Bacterial filtration efficiency (BFE) %99.6499.799.3799.8599.91< 98Pass
4ward, UK - for 5 facegaiters (Filter A) after 100 wash cycles (40°C and tumble dried). On seam test includes standard stitching. Test measures survivability of staphylococcus aureus using a wet aerosol and cascade impactor, size range 0.65um – 7.0um, mean particle 3.0um, velocity 9.6cm/s.

Nelson Labs (USA) - filtration and breathability - ASTM 3502-21 Barrier face coverings

Number of wash cyclesTest filter BSample Number 1Sample Number 2Sample Number 3Sample Number 4Sample Number 5Sample Number 6Sample Number 7Sample Number 8Sample Number 9Sample Number 10
1Filtration %94.1496.0095.3694.1394.3196.6896.5395.0094.6995.05
Airflow Resistance (mm H2O)
50Filtration %98.2297.6898.3898.2798.4397.1697.2196.4998.5697.53
Airflow Resistance (mm H2O)
Nelson Labs, USA - for 10 samples of the facegaiter (Filter B) tested with a TSI 8130 automated filter tester, using a sample holder to allow positioning of whole mask with positive clamping around the edge of the 3-layer filter at or inside of the seal positions. Flow rate = 85L/min, test aerosol NaCl, 50% of the test aerosol by mass is <0.27um and 50% by count is <0.075um. All results meet requirements for level 2 – highest performance level.

Breathability after 1 wash <4.0mm after 50 washes <4.9mm H2O. All results meet requirements for level 2 - highest performance level.

Wearer protection for mask as worn – not to a specific standard:

Filtration efficiency % (0.3-0.5um)
Motion typeN95 Controlfacegaiter - filter A
test run 1test run 2test run 3
Head Nod93.588.086.986.9
Head Shake93.585.582.885.3
Jaw Up & Down92.986.584.788.4
Head Wobble90.884.781.385.1
NC State, USA - one facegaiter fitted and tested three times on an experimental, animated head and shoulder manikin having a range of motions mimicking human movements and pliable artificial skin. The number of ambient particles was increased as required using artificially generated NaCl following the standard fit test protocol. Animation was continuous, with a 1-minute sample time for each motion.

Home Laundry

Testing of the facegaiter by The University of the West of Scotland confirms it is safe to launder the facegaiter in a home washing machine and use it again and again. In testing at 40°C or at 60°C, a typical detergent removed more than 99.99% of bacteria and met the cleanliness requirements for a new single use surgical mask (BS EN14683 Medical Face Masks).

Physiological impact

Multiple studies at The University of the West of Scotland found no significant difference between an FFP2 respirator and the facegaiter in terms of thermal comfort, feelings of breathlessness, heart rate and blood oxygen levels during rest, light and moderate exercise.

Our Partners

Financial Support - We are grateful for the support received from Innovate UK (Project No. 57852), Scottish Funding Council, and the NHS Golden Jubilee Foundation. Views expressed are those of tensARC and not necessarily those of the foregoing.

Standards Committee memberships – BSI TCI/100/02 Community face coverings; ASTM F23.65 Respiratory (ASTM F3502 Barrier face coverings)

To find out more about facegaiter research or to a purchase a facegaiter visit the facegaiter site here...

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