Does this mean office-to-residential conversions are safe?

A specific safety concern about office-to-residential conversions is not verified on this site, so no blanket assurance either way is being made here. Any conversion project has to meet the local building code for residential use, covering things like egress, natural light and ventilation, and gets reviewed by the city or county building department before occupancy. That review process, not a general assumption, is what actually confirms a specific conversion is safe.