Core clauses: First, maintenance subject, must be implemented by certified unit's own personnel, no subcontracting or subletting allowed; Second, prohibited acts, no disguised subcontracting in the name of cooperation, affiliation or delegation; Third, personnel requirements, on-site maintenance personnel must hold certificates and belong to the unit; Fourth, emergency guarantee, maintenance unit 24-hour on-duty, response time ≤30 minutes; Fifth, penalty standards, for subcontracting, confiscate illegal gains, fine 20,000–100,000 yuan; revoke qualification for serious cases.