(If only we knew which one.)
The N95 respirator needs to have a proper fit to be effective. It has to have a tight face fit. And then we do what we call a fit test, which is the employee dons the mask, presses the seal tightly all the way around their nose and mouth. Then we put the large -- we. The employee health nurse is who does this. They put a large plastic hood on top of the employee's head. There's a small hole and there are squirt bottles, if you will, that aerosolize a saccharin solution in different concentrations. And they squirt that saccharin solution and aerosolize it into the hood while the employee is reading a poem. And the words in that poem mimic different facial movements. So the premise is that if they can taste that saccharin at all during that test, they don't have a proper seal.