Fitting a mask is a very important aspect because it can involve some serious problems.
Adjusting your mask
A good fit means that the mask can seal perfectly to the skin. The mask only works when air passes through the filter. The air flows along the path of least resistance, which means that if there is no proper fit, the air will flow back and forth rather than through the mask, reducing the ability to protect.
Check the fit: a basic test that should be done every day
Persons wearing tight-fitting breathing protection devices must perform a sealing inspection each time they wear a mask; in fact, unless the mask is worn voluntarily, national regulations may require this. The fit test ensures that the mask fits properly and provides a firm fit.
The user can perform a seal check under positive or negative pressure: Positive pressure check generally means blocking with both hands and attempting to exhale to block the breathing valve on the half or full cover, or to cover the surface of the device on the particulate filter cover. If slight pressure builds up, there are no air leaks around the edge of the mask. Negative pressure inspection involves either blocking the intake valve on the half or full hood, or covering the surface of the device with a particulate filter mask, usually by hand and trying to breathe. If no air enters, the seal is airtight.
Stability of masks
The better the mask is worn, the more stable it is on the user’s face. The fit test determines the mask’s ability to maintain an adequate seal when the person moves. This is why people who undergo these tests must perform various exercises as part of the test. The mask that moves during movement may not maintain the correct seal.
Compatibility with other PPE
Safety glasses, hearing protection, face shields, industrial helmets and protective clothing can “compete” for face, head or body space. For example, if the mask does not fit properly (especially if it is too big), it can overlap the glasses. And, the more times this happens, the more fog will form on the glasses, so the greater the chance that it will interfere with the seal of the mask. For more information, refer to the product instructions.
To find these problems, coordination test regulations require that any PPE that might interfere with the mask seal be worn during the coordination test.