Respiratory Protection Image
The researchers achieved a close-fitting seal between the mask shell and the face using 3D-printed softened silicone, to deliver nine mask prototypes. (Credit: Kings College London)

New research has demonstrated the feasibility of mass producing customized respiratory protection for healthcare workers with a comfortable close-fitting seal that is suitable for nearly 90 percent of face shapes and sizes.

Providing adequate filtering PPE for frontline healthcare workers has been a major challenge since the start of the pandemic, and the key issue in providing effective protection is the need for a close-fitting seal between the mask and the face.

However, achieving mask fit across the full range of face sizes and shapes has proven difficult, and ‘fit-test’ failure remains a commonly reported occurrence. The areas of greatest variability, and where fit is most difficult to achieve, are around the nose, chin, and cheeks.

The researchers captured three-dimensional face measurements from 200 people, with mixed facial form, gender and ethnicity, to ensure their sample was representative of the different facial shapes. They then performed statistical analysis that showed that a large proportion of people (87.5 percent) can be categorized into a relatively small number (nine) of designs for a rigid mask shell with an approximate fit to the person’s face.

The researchers achieved a close-fitting seal between the mask shell and the face using 3D-printed softened silicone, to deliver nine mask prototypes. The fit of each of these prototypes was demonstrated using a novel method to detect whether vapor could escape from the mask. The researchers further tested these designs on volunteer clinicians who had failed fit tests with commercially available half-mask respirators; each passed standard qualitative fit testing using the closest prototype available.

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