When tightening the straps on the self-contained breathing apparatus facepiece, which straps should always be tightened first?

When tightening the straps on the self-contained breathing apparatus facepiece, which straps should always be tightened first?

• A. lower
• B. temple
• C. upper
• D. harness

Answer: (A)

Titting the bottom straps first is essential because it establishes the seal where leaks are most likely to start—the chin and jawline. By snugging the lower straps, the facepiece is pulled against the face from the bottom, creating a solid base seal. After that, tightening the upper straps draws the rest of the mask toward the face, completing the seal around the cheeks, nose, and forehead. The harness on the SCBA is for securing the unit to the body, not for forming the facial seal, so it’s adjusted after the mask is sealed. Starting with the upper straps can cause the mask to shift and fail to seal properly at the bottom.

Titting the bottom straps first is essential because it establishes the seal where leaks are most likely to start—the chin and jawline. By snugging the lower straps, the facepiece is pulled against the face from the bottom, creating a solid base seal. After that, tightening the upper straps draws the rest of the mask toward the face, completing the seal around the cheeks, nose, and forehead. The harness on the SCBA is for securing the unit to the body, not for forming the facial seal, so it’s adjusted after the mask is sealed. Starting with the upper straps can cause the mask to shift and fail to seal properly at the bottom.