Detail of GB/T 25915.1-2021

Introduction of GB/T 25915.1-2021

Cleanrooms and associated controlled environments - Part 1: Classification of air cleanliness by particle concentration 1 Scope This document specifies the classification of air cleanliness in terms of concentration of airborne particles in cleanrooms and clean zones; and separative devices as defined in GB/T 25915.7. Only particle populations having cumulative distributions based on threshold (lower limit) particle sizes ranging from 0.1 µm to 5 µm are considered for classification purposes. Concentrations of ultrafine particles (particles smaller than 0.1 µm) will be addressed in a separate standard to specify air cleanliness by nano-scale particles. The use of light scattering (discrete) airborne particle counters (LSAPC) is the basis for determination of the concentration of macroparticles (particles larger than 5 µm) at designated sampling locations. An M descriptor may be used to quantify populations of the macroparticles. This document cannot be used to characterize the physical, chemical, radiological, viable or other nature of airborne particles. 2 Normative references The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. GB/T 25915.2-2021 Cleanrooms and associated controlled environments - Part 2: Monitoring to provide evidence of cleanroom performance related to air cleanliness by particle concentration (ISO 14644-2:2015, IDT) GB/T 25915.7 Cleanrooms and associated controlled environments - Part 7: Separative devices (clean air hoods, gloveboxes, isolators and minienvironments) (GB/T 25915.7-2020, ISO 14644-7:2004, IDT) GB/T 29024.4-2017 Determination of particle size distribution - Single particle light interaction methods - Part 4: Light scattering airborne particle counter for clean spaces (ISO 21501-4:2007, IDT)   3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 General 3.1.1 cleanroom room within which the number concentration of airborne particles is controlled and classified, and which is designed, constructed and operated in a manner to control the introduction, generation and retention of particles inside the room Note 1: The class of airborne particle concentration is specified. Note 2: Levels of other cleanliness attributes such as chemical, viable or nanoscale concentrations in the air, and also surface cleanliness in terms of particle, nanoscale, chemical and viable concentrations might also be specified and controlled. Note 3: Other relevant physical parameters might also be controlled as required, e.g. temperature, humidity, pressure, vibration and electrostatic. 3.1.2 clean zone defined space within which the number concentration of airborne particles is controlled and classified, and which is constructed and operated in a manner to control the introduction, generation and retention of contaminants inside the space Note 1: The class of airborne particle concentration is specified. Note 2: Levels of other cleanliness attributes such as chemical, viable or nanoscale concentrations in the air, and also surface cleanliness in terms of particle, nanoscale, chemical and viable concentrations might also be specified and controlled. Note 3: A clean zone(s) can be a defined space within a cleanroom or might be achieved by a separative device. Such a device can be located inside or outside a cleanroom. Note 4: Other relevant physical parameters might also be controlled as required, e.g. temperature, humidity, pressure, vibration and electrostatic. 3.1.3 installation cleanroom or one or more clean zones, together with all associated structures, air-treatment systems, services and utilities 3.1.4 classification method of assessing level of cleanliness against a specification for a cleanroom or clean zone Note: Levels shall be expressed in terms of an ISO Class, which represents maximum allowable concentrations of particles in a unit volume of air. 3.2 Airborne particles 3.2.1 particle minute piece of matter with defined physical boundaries 3.2.2 particle size diameter of a sphere that produces a response, by a given particle-sizing instrument that is equivalent to the response produced by the particle being measured Note: For discrete-particle light-scattering instruments, the equivalent optical diameter is used. 3.2.3 particle concentration number of individual particles per unit volume of air 3.2.4 particle size distribution cumulative distribution of particle concentration as a function of particle size 3.2.5 macroparticle particle with an equivalent diameter greater than 5 µm 3.2.6 M descriptor designation for measured or specified concentration of macroparticles per cubic metre of air, expressed in terms of the equivalent diameter that is characteristic of the measurement method used Note: The M descriptor can be regarded as an upper limit for the averages at sampling locations. M descriptors cannot be used to define ISO Classes, but the M descriptor may be quoted independently or in conjunction with ISO Classes. 3.2.7 unidirectional airflow controlled airflow through the entire cross-section of a cleanroom or a clean zone with a steady velocity and airstreams that are considered to be parallel 3.2.8 non-unidirectional airflow air distribution where the supply air entering the cleanroom or clean zone mixes with the internal air by means of induction   3.3 Occupancy states 3.3.1 as-built condition where the cleanroom or clean zone is complete with all services connected and functioning but with no equipment, furniture, materials or personnel present 3.3.2 at-rest condition where the cleanroom or clean zone is complete with equipment installed and operating in a manner agreed upon, but with no personnel present 3.3.3 operational agreed condition where the cleanroom or clean zone is functioning in the specified manner, with equipment operating and with the specified number of personnel present 3.4 Testing instrumentation 3.4.1 resolution smallest change in a quantity being measured that causes a perceptible change in the corresponding indication Note: Resolution can depend on, for example, noise (internal or external) or friction. It may also depend on the value of a quantity being measured. [Source: ISO/IEC Guide 99:2007, 4.14] 3.4.2 maximum permissible measurement error extreme value of measurement error, with respect to a known reference quantity value, permitted by specifications or regulations for a given measurement, measuring instrument, or measuring system Note 1: Usually, the term “maximum permissible errors” or “limits of error” is used where there are two extreme values. Note 2: The term “tolerance” shall not be used to designate “maximum permissible error”. [Source: ISO/IEC Guide 99:2007, 4.26] 3.5 Instrument specifications 3.5.1 light scattering (discrete) airborne particle counter; LSAPC instrument capable of counting and sizing single airborne particles and reporting size data in terms of equivalent optical diameter Note: The specifications for the LSAPC are given in GB/T 29024.4-2017. 3.5.2 discrete-macroparticle counter instrument capable of counting and sizing single airborne macroparticles Note: See Table F.1 for specifications. 3.5.3 time-of-flight particle sizing apparatus discrete-particle counting and sizing apparatus that defines the aerodynamic diameter of particles by measuring the time for a particle to accommodate to a change in air velocity Note 1: This is usually done by measuring the particle transit time optically after a fluid stream velocity change. Note 2: See Table F.2 for specifications.

Contents of GB/T 25915.1-2021

Forward i Introduction iv 1 Scope 2 Normative references 3 Terms and definitions 4 Classification 5 Demonstration of compliance Annex A (Normative) Reference method for classification of air cleanliness by particle concentration Annex B (Informative) Examples of classification calculations Annex C (Informative) Counting and sizing of airborne macroparticles Annex D (Informative) Sequential sampling procedure Annex E (informative) Specification of intermediate decimal cleanliness classes and particle size thresholds Annex F (Informative) Test instruments Bibliography