The line runs between damage and defect. If a system discharges and ruins a tenant’s inventory, general liability is in the conversation. If the system was designed wrong and has to be reworked, the cost of the rework is a professional exposure, and most standard contractor forms exclude it outright. The awkward cases are the ones where both are true at once — the design error causes the damage — and then the two policies have to be read together.
Where the professional exposure actually shows up:
Hydraulic calculations. A calculation that does not deliver required density at the remote area is a professional error, whether it is caught at plan review or after a fire.
Head spacing and coverage area. Obstruction rules and spacing limits are judgment calls made by your designer. A gap found during acceptance testing is rework; a gap found during a fire is a claim.
Hazard classification. Designing an ordinary hazard system for what turns out to be an extra hazard occupancy is a design decision, not faulty workmanship.
Inspection reports. A deficiency you had an obligation to note and did not is an omission, and it surfaces years later when somebody pulls the file.
How Liberty structures your protection:
Errors and omissions comes with Liberty’s fire protection program by endorsement rather than being quoted as an afterthought, so a design claim has a policy to land in instead of a coverage argument.