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Users of SCOTT SAFETY SCBA Full Facepiece: AV-3000 SureSeal, AV-3000 HT, AV-2000, and other similar designs

Dislodged Sizing Dot Inside Regulator Diaphragm

Recently one of our firefighters experienced smoke inhalation during a training incident. The exposure was caused by a dislodged sizing dot found wedged in the regulator diaphragm. This allowed outside contaminated air to enter into the mask.

The sizing dots are originally attached by adhesive during the manufacturing process. They are black or color coded by size. Figure 1 shows the sizing dots as they come from the manufacturer. Figure 2 shows a mask with missing sizing dots.

A sizing dot migrated into the regulator opening and then into the interior diaphragm. This prevented the diaphragm from closing completely. Figure 3 shows the actual component discovered with the sizing dot wedged inside.


Immediate actions:

  •  Check the mask to ensure that all four sizing dots are in place.
  •  Check the opening of the regulator with a flashlight for loose sizing dots.
  •  Perform a standard inspection, don the SCBA, and breathe air to ensure that the regulator is working correctly. This includes breathing down the air in the system while the bottle is turned off.
  •  Inspect the mask bag for debris and cleanliness
  •  Assign a certified technician to inspect the internal components of the regulator.
  •  Replace all sizing dots by contacting the SCOTT service representative.
  •  Immediately remove the unit from service if there is a performance failure.


  •  Store the mask by itself in a designated, clean mask bag.
  •  Store SCBA regulators:
  •  Attached to a mask and inserted in a mask bag
  •  Attached to the SCBA belt mounted regulator holder
  •  Inserted into a mask bag or a clean, clear, and sealed bag

During fire ground operations:

  •  Special care should be used to keep debris from contaminating and accumulating in the mask and regulator opening.
  •  If separated from the regulator, keep the mask in the mask bag and the regulator clipped to the waist belt holder.
  •  If connected to the regulator, insert both pieces in the mask bag and clip the mask bag drawstring to the bunker coat.
  •  Visually inspect the mask for dislodged sizing dots, foreign material, and other debris.

Department policy and procedures:

  • Clean the regulator after every use according to manufacturer recommendations.
  •  Develop a mask bag exchange program during fire ground operations to reduce bag contamination.
  •  Evaluate SCBA donning procedures. Ensure that breathing down the air supply to check the seal is part of the donning procedures. Refer to the Scott manual for specifics.