Contractor Proposes Wet Removal of Friable Insulation Without Local Exhaust
A project involves removing approximately 300 linear feet of friable thermal system insulation from a boiler room with limited ventilation and a single doorway. The contractor proposes wet removal methods with amended water and drop cloths but no local exhaust ventilation (negative air machines), arguing the space is small and the material will stay wet. The room shares a corridor with occupied offices through a door that is not sealed in the proposal. The designer must evaluate whether the proposed method meets the intent of the specification and worker/occupant protection requirements.
1. Evaluate the contractor's proposal. What deficiencies must the designer flag?
Read the worked answer
The proposal is deficient on containment and engineering controls. Friable thermal system insulation removal generates fibers even when wet, and the absence of negative air machines with HEPA filtration means the containment cannot maintain negative pressure relative to adjacent spaces. The unsealed corridor door is a direct migration pathway to occupied offices. Wet methods reduce but do not eliminate fiber release.
The designer should require: a sealed containment with critical barriers at the doorway and any openings; negative air machines sized to the containment volume maintaining negative pressure; HEPA filtration; and monitoring to confirm containment integrity. The contractor's 'small space' argument does not substitute for engineering controls. The design should specify these as mandatory, not optional, and the contractor must revise the work plan before mobilization.
2. How should the designer respond if the contractor claims negative air machines are impractical in the space?
Read the worked answer
The designer should not waive the requirement. If physical constraints exist, the designer evaluates alternatives that preserve the protective intent - e.g., additional critical barriers, a portable negative pressure unit placed at the doorway with ducting, or sequencing work when adjacent spaces are unoccupied - but the objective (containment under negative pressure, no fiber migration) is non-negotiable. Any deviation must be documented as an approved equal with justification and must still meet worker protection and occupant protection standards.
The response should be in writing, reference the specification requirement, and require a revised plan. If the contractor cannot meet the requirement, the designer should consider whether the work can proceed at all under the current scope or must be re-sequenced.