• Cover the openings at the bottom of the outlet valve cover with the palm of one hands.
• Breathe out forcefully so the air escapes around the edges of the faceplace.

Check the mask for leaks.

• Press your palm over the opening in the canister coupling to seat the canister.
• Inhale lightly. If the mask collapses against your face and remains so while you hold your breath, the mask is airtight. If the mask does not collapse, check for hair or clothing between the mask and your face.