This document discusses sources of contamination in sterile manufacturing facilities. It identifies potential sources as facilities, flows, equipment, cleaning, personnel, utilities, and processes. Specific microorganisms found in air, water, equipment, and humans are outlined. Proper facility design, including layout, materials of construction, HVAC, and utilities are described. Human behavior and proper training are important to avoid contamination issues. Effective cleaning requires the right tools, temperature, time, concentration and antimicrobial agents. Molds can grow where there is moisture, nutrients and suitable temperature. Proper decontamination of classified environments and clean room design are also covered.