This Standard provides technical criteria and guidelines for the in-service inspection, care, repair or replacement, testing, and recertification of PVHOacrylic windows in Pressure Vessels for Human Occupancy. It is intended to be used only with acrylic windows designed, constructed, tested, and certified in accordance with the requirements of ASME PVHO-1, Safety Standard for Pressure Vessels for Human Occupancy. This Standard provides technical criteria for the user to establish the serviceability of a PVHO acrylic window under its specific environmental service conditions. Windows in protected environments as well as those in severe environments are addressed. Judicious use of this Standard will allow the user and/or the jurisdictional authority to determine when a PVHO acrylic window requires replacement.