e.g. a Class M3 room has a particle limit for particles ³ 0.5 m m of 1000/m^3. This is shown in Table 3.
With a little thought it can be appreciated that the airborne contamination level of a given cleanroom is dependent on the particle generating activities going on in the room. If a room is empty, a very low particle concentration can be achieved, this closely reflects the quality of air supplied by the high efficiency filter. If the room has production equipment in it and operating, there will be a greater particle concentration but the greatest concentrations will occur when the room is in full production. The classification of the room according to FS 209D may therefore be carried out when the room is:
Table 2 Federal Standard 209D Class Limits
CLASS
MEASURED PARTICLE SIZE (MICROMETERS)
0.1
0.2
0.3
0.5
5.0 1
35
7.5
3
1
NA
10
350
75
30
10
NA
100
NA
750
300
100
NA
1,000
NA
NA
NA
1,000
7
10,000
NA
NA
NA
10,000
70
100,000
NA
NA
NA
100,000
700
Table 3 Federal Standard 209E Airborne Particulate Cleanliness Classes
Class Name
Class Limits 0.1m m 0.2m m 0.3m m 0.5m m 5m m Volume Units Volume Units Volume Units Volume Units Volume Units SI English (m^3) (ft^3) (m^3) (ft^3) (m^3) (ft^3) (m^3) (ft^3) (m^3) (ft^3) M 1 350 9.91 75.7 2.14 30.9 0.875 10.0 0.283 -- -- M 1.5 1 1 240 35.0 265 7.50 106 3.00 35.3 1.00 -- -- M 2 3 500 99.1 757 21.4 309 8.75 100 2.83 -- -- M 2.5 10 12 400 350 2 650 75.0 1 060 30.0 353 10.0 -- -- M 3 35 000 991 7 570 214 3 090 87.5 1 000 28.3 -- -- M 3.5 100 -- -- 26 500 750 10 600 300 3 530 100 -- -- M 4 -- -- 75 700 2 140 30 900 875 10 000 283 -- -- M 4.5 1 000 -- -- -- -- -- -- 35 300 1 000 247 7.00 M 5 -- -- -- -- -- -- 100 000 2 830 618 17.5 M 5.5 10 000 -- -- -- -- -- -- 353 000 10 000 2 470 70.0 M 6 -- -- -- -- -- -- 1 000 000 28 300 6 180 175 M 6.5 100 000 -- -- -- -- -- -- 3 350 000 100 000 24 700 700 M 7 -- -- -- -- -- -- 10 000 000 283 000 61 800 1 750
(a) as built, ie complete and ready for operation, with all services connected and functional but without production equipment or operating personnel.
(b) at rest, ie complete, with all services functioning and with equipment installed and operable or operating, as specified but without personnel in the facility.
(c) operational, ie in normal operation, with all services functioning and with equipment and personnel, if applicable, present and performing their normal work functions in the facility.
Federal Standard 209 is a document which mainly gives information on the airborne particle limits that are required to specify the airborne quality of cleanrooms and also gives the methods used to check what concentrations are present. It does not give any information on how a cleanroom should be operated. This information had been included in a series of Recommended Practices which are written by the same Institute as has written the Federal Standard 209, namely the Institute of Environmental Sciences. Some of the RP's which are of particular interest to those who test and run cleanrooms are discussed later in this document.
British Standard 5295:1989
This standard is available from:B S I Standards
389 Chiswick High Road
London W44 AL
Tel 0181 996 9000
Fax 0181 996 7400
The British Standard is in five parts. These are:
Part 0 - General introduction and terms and definitions for cleanrooms and clean air devices. (4 pages)
Part 1 - Specification for cleanrooms and clean air devices. (14 pages)
Part 2 - Method for specifying the design, construction and commissioning of cleanroom and clean air devices. (14 pages)
Part 3 - Guide to operational procedures and disciplines applicable to cleanrooms and clean air devices. (6 pages)
Part 4 - Specification for monitoring cleanrooms and clean air devices to prove continued compliance with BS 5295. (10 pages)
The contents of the above parts are as follows:
Part 0 - 'General introduction, terms and definitions for cleanrooms and clean air devices'
The definitions have been drawn together and presented in this section. This part also provides a basic introduction to the main parts of the standard, particularly for those unfamiliar with cleanrooms or the standard itself.
Part 1 - 'Specification for cleanrooms and clean air devices'
The Standard contains ten classes of environmental cleanliness. Shown in Table 4 are the classes given in the standard. All classes have particle counts specified for at least two particle size ranges to provide adequate confidence over the range of particle size relevant to each class.
Some classes of rooms, except for 0.3 m m particles, have an identical specification. For example, Class F is equivalent to Class E except for the 0.3 m m particle specification. This is deliberate, as many users, e.g. pharmaceutical manufacturing, do not wish to be associated with the small particle technology that is not appropriate to their industry.
BS 5295:1989 identifies three states of operation similar to FS208E:Table 4 BS 5295 Environmental cleanliness classes
Maximum permitted number of particles per m^3 (equal to, or greater than, stated size) Maximum floor area per sampling position for cleanrooms (m^2) Minimum pressure difference* Class of environmental cleanliness 0.3 m m 0.5 m m 5 m m 10 m m 25 m m Between classified areas and unclassified areas (Pa) Between classified area and adjacent areas of lower classification (Pa) C D E F G H J K L M
- as built - on completion, prior to moving in
- unmanned - operational but not in use
- manned - in full operational use
- Also given in the specification of Part 1 are other requirements for cleanrooms to comply with. These are:
- minimum pressure difference between the cleanroom and adjacent areas (see Table 4)
- filter installation test leakage
- freedom of leakage from construction joints or openings
Part 2 - 'Method for specifying the design, construction and commissioning of cleanrooms and clean air devices'
A major consideration in the rewrite of BS 5295 was to ensure its usefulness as a purchase and operational specification and as supporting documentation to a contract. Part 2 has therefore been restructured into a format which enables a purchaser to specify what type of room or device is required and, where relevant, how it is to be achieved. To assist with its use as part of contractual documentation it has been given specification status, i.e. it is mandatory.
Part 3 - 'Guide to operational procedures and disciplines applicable to cleanroom and clean air devices'
This incorporates guidance for those drawing up procedures for personnel, operations, cleaning, garments and garment laundering.
Part 4 - 'Specification for monitoring cleanrooms and clean air devices to prove continued compliance with BS 5295: Part 1'
Cleanroom and clean air equipment standards have for many years defined classes of cleanliness and how they are to be assessed. However there has never been any requirement to test a cleanroom at any point in its often very long lifetime, other than at the time of handover from supplier to purchaser. Once accepted from the supplier, the facility then repaid its capital cost, over a life span of ten to twenty years, sometimes without ever being tested. Yet over this period customers were provided with products which were stated to be 'produced under Class X'. This can no longer be the case.
The tests specified are those contained in Part 1, thus providing a continuity back to the original purchase specification. The intervals between tests are related to the class of room or device and are given later in this manual in that section relating to the validation and testing of cleanrooms.
ISO Standard
Because of the large number of cleanroom standards produced by individual countries it is very desirable that one world-wide standard of cleanroom classification is produced. The International Standards Organisation is producing such a document. Because of the number of countries involved and the problems with translation it may be over a year before it is published. However, it is unlikely that it will be different from table 5.Table 5. Selected ISO 209 airborne particulate cleanliness classes for cleanrooms and clean zones.
numbers (N) Maximum concentration limits (particles/m^3 of air) for particles equal to and larger than the considered sizes shown below
0.1m m
0.2m m
0.3m m
0.5m m
1m m
5.0m m
ISO 1
ISO 2
ISO 3
ISO 4
ISO 5
ISO 6
ISO 7
ISO 8
ISO 9
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