What if an FSD sleeve gap is packed with regular fiberglass?

Regular insulation is not automatically an approved firestop. Stop cover, verify the listed assembly/firestop system, and replace improper packing with the approved material/detail.

['The gap around a damper sleeve through a rated wall is part of a listed/rated assembly. If someone stuffed it with random fiberglass, it may look filled but still fail inspection or life-safety requirements.', 'Do not guess the firestop product from memory. Check the damper installation instructions, wall rating, approved firestop submittal/UL system, and project detail. The likely fix is to remove the wrong material and install the approved mineral wool/firestop/wrap/caulk system exactly as specified.']

Stop if

• Use this as training guidance. The foreman, approved drawings, project specs, manufacturer installation instructions, employer safety policy, and AHJ/code requirements always control the final answer.

Check

• Improper firestopping around a damper sleeve can fail inspection and compromise a rated assembly.

Steps

• Confirm wall rating, damper type, sleeve, retaining angles, and gap condition.
• Check the damper manufacturer installation sheet and approved firestop detail/submittal.
• Identify whether the existing material is approved for that exact assembly.
• Stop wall/shaft cover until the firestop condition is corrected and documented.
• Take photos before and after correction for inspection/closeout.

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