1. (N) A maintenance schedule is in place.2. (N) Maintenance is on schedule.3. (N) All deferred maintenance is logged, given justification, and rescheduled.4. (N) All filters, purifiers and other such equipment needing periodic cleaning or replacement are tagged with a control number, the date of last action, and the date of next action.5. (N) Maintenance checks include inspection for visible signs for need to repair.6. (+) Supplier can demonstrate at least 2 years of maintenance records."