FED-STD-209 Revision E:1992

1 Scope and limitations
1.1 Scope
1.2 Limitations
2 Referenced documents
3 Definitions
3.1 Airborne particulate cleanliness class
3.2 Anisokinetic sampling
3.3 Calibration
3.4 Clean zone
3.5 Cleanroom
3.5.1 As-built cleanroom (facility)
3.5.2 At-rest cleanroom (facility)
3.5.3 Operational cleanroom (facility)
3.6 Condensation nucleus counter (CNC)
3.7 Discrete-particle counter (DPC)
3.8 Entrance plane
3.9 Isoaxial
3.10 Isokinetic sampling
3.11 Monitoring
3.12 Nonunidirectional airflow
3.13 Particle
3.14 Particle concentration
3.15 Particle size
3.16 Student's t statistic
3.17 U descriptor
3.18 Ultrafine particles
3.19 Unidirectional airflow
3.20 Upper confidence limit (UCL)
3.21 Verification
4 Airborne particulate cleanliness classes and
           U descriptors
4.1 Class listed in Table I
4.1.1 Measurement at particle sizes listed in Table
           I
4.1.2 Measurement at alternative particle sizes
4.2 Provision for defining alternative airborne
           particulate cleanliness classes
           Table I. Airborne particulate cleanliness
           classes
4.3 Provision for describing ultrafine particle
           concentrations (U descriptors)
4.4 Nomenclature for airborne particle
           concentrations
4.4.1 Format for airborne particulate cleanliness
           classes
4.4.2 Format for U descriptors
5 Verification and monitoring of airborne
           particulate cleanliness
5.1 Verification of airborne particulate
           cleanliness
5.1.1 Frequency
5.1.2 Environmental test conditions
5.1.2.1 State of cleanroom or clean zone during
           verification
5.1.2.2 Environmental factors
5.1.3 Particle counting
5.1.3.1 Sample locations and number: unidirectional
           airflow
5.1.3.2 Sample locations and number:
           nonunidirectional airflow
5.1.3.3 Restrictions on sample locations
5.1.3.4 Sample volume and sampling time
5.1.3.4.1 Single sampling plan for classes in Table I
5.1.3.4.2 Single sampling plan for alternative classes
           or particle sizes
5.1.3.4.3 Single sampling plan for U descriptors
5.1.3.4.4 Sequential sampling plan
5.1.4 Interpretation of the data
5.2 Monitoring of airborne particulate
           cleanliness
5.2.1 Monitoring plan
5.2.2 Particle counting for monitoring
5.3 Methods and equipment for measuring airborne
           particle concentrations
5.3.1 Counting particles 5 micrometers and larger
5.3.2 Counting particles smaller than 5 micrometers
5.3.3 Counting ultrafine particles
5.3.4 Limitations of particle counting methods
5.3.5 Calibration of particle counting
           instrumentation
5.4 Statistical analysis
5.4.1 Acceptance criteria for verification
5.4.2 Calculations to determine acceptance
5.4.2.1 Average particle concentration at a location
5.4.2.2 Mean of the averages
5.4.2.3 Standard deviation of the averages
5.4.2.4 Standard error of the mean of the averages
5.4.2.5 Upper confidence limit (UCL)
           Table II. UCL factor for 95% upper confidence
           limit
5.4.2.6 Sample calculation
6 Recommendation for changes
7 Conflict with referenced documents
8 Federal agency interests
Appendix A - Counting and sizing airborne particles
             using optical microscopy
A10 Scope
A20 Summary of the method
A30 Equipment
A40 Preparation of equipment
A50 Sampling the air
A60 Calibration of the microscope
A70 Counting and sizing particles by optical
           microscopy
A80 Reporting
A90 Factors affecting precision and accuracy
Appendix B - Operation of a discrete-particle counter
B10 Scope and limitations
B20 References
B30 Summary of method
B40 Apparatus and related documentation
B50 Preparation for sampling
B60 Sampling
B70 Reporting
Appendix C - Isokinetic and anisokinetic sampling
C10 Scope
C20 Reference
C30 Background
C40 Methods
           Figure C.1. Probe inlet diameters (metric
           units) for isokinetic sampling, v = vo
           Figure C.2. probe inlet diameters (English
           units) for isokinetic sampling, v = vo
           Figure C.3. Contours of sampling bias,
           c/co = 0.95, 1.05
C50 Example
Appendix D - Method for measuring the concentration of
             ultrafine particles
D10 Scope
D20 References
D30 Apparatus
           Figure D.1. Envelope of acceptability for the
           counting efficiency of a DPC used to verify
           the U descriptor
D40 Determining the concentration of ultrafine
           particles
Appendix E - Rationale for the statistical rules used in
             FED-STD-209E
E10 Scope
E20 The statistical rules
E30 Sequential sampling
E40 Sample calculation to determine statistical
           validity of a verification
Appendix F - Sequential sampling: an optional method for
             verifying the compliance of air to the
             limits of airborne particulate cleanliness
             classes M 2.5 and cleaner
F10 Scope
F20 References
F30 Background
F40 Method
           Figure F.1. Observed count, C, vs. expected
           count, E, for sequential sampling
           Table F.1. Upper and lower limits for time at
           which C counts should arrive
F50 Examples
F60 Reporting
Appendix G - Sources of supplemental information
G10 Scope
G20 Sources of supplemental information

Gives classes of air cleanliness for airborne particulate levels in cleanrooms and zones. Gives methods for class verification and monitoring of air cleanliness. Coverage includes: airborne particulate cleanliness classes and U descriptions; verification and monitoring of airborne particulate cleanliness. Also contains detailed definitions and appendices.

This document establishes standard classes, and provides for alternative classes, of air cleanliness for cleanrooms and clean zones based on specified concentrations of airborne particles. It prescribes methods for verifying air cleanliness and requires that a plan be established for monitoring air cleanliness. It also provides a method for determining and describing concentrations (U descriptors) of ultrafine particles.