SOPs for equipment operation, maintenance, and calibration can also be put in written form fairly quickly because very often the equipment manuals provide the detailed information needed. However, the requirement for written procedures is not limited to the production method, equipment operation and test methods. The more difficult SOPs to prepare are those describing control of materials at every stage, monitoring of storage conditions, requirements for storage segregation, SOPs for gowning, cleaning, fumigating the facility, monitoring equipment, monitoring the facility air and surfaces, SOPs for entry of materials in and out of the clean and aseptic areas, SOPs for personnel health and hygiene, animal care SOPs (raising, feeding, treating, health, cleaning and maintenance of animal facilities, cage washing, quarantine of animals, etc.), SOPs for testing cell, viral and bacterial characteristics, SOP for egg candling, SOPs for self-inspections and audits, SOPs for sampling, and even an SOP for writing, revising SOPs, and one for controlling the distribution of all the other SOPs.