Mask Exhalation Valve Seal
Making a face mask with an exhalation valve safer for use
Many face masks including N95 masks used for industrial and home use (eg 3M 8511) have exhalation valves so exhaled air goes directly out the valve unfiltered so the face is cooler.
This makes masks with exhalation valves not suitable for use when trying to reduce the spread of COVID-19 and other diseases to other people. This includes staff in aged care, carers for elderly or immune compromised people, and people with symptoms of COVID-19 or other diseases.
A seal for the mask exhalation valve can easily made be made from foam tape or vinyl sheet with adhesive on one side., which sticks over the exhalation valve to block it.
For the 3M 8511 N95 face mask, a seal can easily made by cutting out a circular disk 22mm (7/8 in) in diameter from foam tape or vinyl sheet and sticking it over the back of the exhalation valve on the inside of the mask.
I used Suntuf Purlin Tape (25mm wide 3mm thick 20m long) available from Bunnings in Australia. This is sufficient to make 800 seals costing 2c each.
Small quantities can be cut out with scissors using a 10c piece as a template. For large quantities a 22mm hollow punch can be used available from tool suppliers.
A seal can also be made from adhesive vinyl sheet , commonly called "contact" used for covering books and making stencils and stickers. This can be cut into 22mm circles using scissors or using a vinyl cutter such as the Brother Scan N Cut