The scramble to supply high-grade face masks to health workers is a familiar story throughout the UK, but getting hold of a mask is only half the battle – unless the mask fits snugly, it’s as protective against Covid-19 as a cotton hankie.

The University of Bath is assisting Avon and Wiltshire Mental Health Partnership (AWP) NHS Trust to ensure its masks fit staff correctly by manufacturing and bottling the chemical solutions needed for ‘fit tests’. NHS supplies of these relatively simple solutions are running low.

Word of the University’s assistance to AWP has already spread to Royal United Hospitals (RUH) Bath NHS Trust, and they too are now asking for supplies of fit-test solutions. Dr Matthew Jones, lecturer in Pharmacy Practice at Bath, said the University would be happy to create batches of the solutions for other NHS organisations in and around Bath, if a need is expressed.

A mask-fit check is essential for staff on the frontline and their patients, says Dr Jones. “The point is to be sure there are no gaps around the sides when a mask is on, and everyone’s face is a different shape and size, so a fitting is essential,” he explained.

A fit test involves fitting a person with a mask, covering their head with a hood and then exposing them to a mist of chemicals that are harmless but strong tasting. If the subject can sense the chemical, the mask is ill-fitting. Two different chemicals are available for the test, in case someone cannot taste one of them. Either a solution containing the sweetener saccharine is sprayed beneath the hood, or one containing Bitrex®. Bitrex® is the most bitter chemical known to science and is added to bleach to stop children drinking it accidentally.

“Our job at the University is to weigh out the right amounts of saccharine and Bitrex®, in a carefully controlled way and then dissolve it in water,” said Dr Jones. “This is completely within the capability of our labs. It helps that we have some very advanced instruments, which are not routinely available in the NHS. We use these to confirm the quality of what we make".

The University has already made and bottled its first batch of fit-test solutions. These were sent to AWP late last week. AWP provides inpatient and community mental health services across Bath and North East Somerset, Swindon, Wiltshire, Bristol, North Somerset and South Gloucestershire. The University’s fit-test solutions will be shared across the Trust’s sites.

Dr Jones said: "We're delighted to be able to use our expertise and the University's facilities to support the NHS's response to Covid-19. I teach Pharmacy students how to manufacture small batches of medicines, so it's personally gratifying to be able to put these techniques to good use."

Ollie Tovey, Emergency Preparedness, Resilience and Response (EPRR) manager at AWP, added: "Across the trust, staff members need to wear Filter Face Protection Level 3 (FFP3) masks in specific situations. Being able to test the fit of these masks is critical to ensuring staff and patient safety, and we are extremely grateful to the University of Bath for their help in making the solution.”

The University’s fit-test solutions are being made, tested and dispatched by a consortium of Bath scientists from the Faculty of Science including the Departments of Biology and Biochemistry, Chemistry, and Pharmacy and Pharmacology, as well as the Material and Chemical Characterisation Facility. The recipes for the two solutions were shared with the University by scientists at the University of Southampton, who have been providing fit-test solutions to hospitals in their neighbourhood.