9. Cleanroom Testing and Monitoring

1. 9. Cleanroom Testing and Monitoring

2. Purposes for initial test: • Fulfill the design • working correctly and achieving the contamination standards • Bench-mark: • establish the initial performance of the room to compare the results of routine check or contamination problem in the future. • Training the staff: (most important) • initial testing is to familiarize and train the staff. • Only opportunity to understand how their cleanroom works and learn the methods used to test.

3. initial test • Time • been built/ going to hand over/ reopen • Tested standards • ISO 14644-1. • Monitoring • to regularly check the room at the time intervals set by ISO 14644-2

4. Principles of Cleanroom Testing • Quantity: • Turbulently: dilute--air volume (supply and extract) • Unidirectional: remove –air velocity • Direction (flow direction): • from clean area  less-clean areas to minimise the movement of contaminated air. • Quality: • the air will not add significantly to the contamination within the room • Distribution inside cleanroom • the air movement has no areas with high concentrations of contamination.

5. Cleanroom Tests

6. Air supply and extract quantities • turbulently ventilated cleanrooms the air supply and extract volumes • unidirectional airflow  air velocity. • Air movement control between areas: direction • The pressure differences between areas are correct. • The air direction through doorways, hatches, etc. is from clean to less-clean.

7. Filter installation leak test • a damaged filter • between the filter and its housing or • any other part of the filter installation. • Containment leak testing • Contamination is not entering the cleanroom through its construction materials.

8. Air movement control within the room • turbulently ventilated : check that there are no areas within the room with insufficient air movement. • unidirectional airflow : check that the air velocity and direction throughout the room is that specified in the design. • Airborne particles and microbial concentrations • final measurements of the concentration of particles and micro-organisms

9. Additional tests • temperature • relative humidity • heating and cooling capabilities of the room • sound levels • lighting levels • vibration levels.

10. requirements • Guides provided by • the American Society Heating Refrigeration and Airconditioning Engineers (ASHRAE) in the USA, and • the Chartered Institute of Building Services Engineers (CIBSE) in the UK.

11. Testing in Relation to Room Type and Occupation State • The type of tests to be carried out in a cleanroom depends on whether the room is unidirectional, turbulent or mixed airflow: • ‘as-built’ ---in the empty room, • ‘at rest’ --- the room fitted with machinery but no personnel present or • ‘fully operational’---these occupancy states are discussed more fully in Section 3.4 of this book.

12. Re-testing to Demonstrate Compliance • The cleanroom checked intervals, these intervals being more frequent in higher specified rooms: ISO 14644-2

13. Monitoring of Cleanrooms • Use risk assessment to decide what monitoring tests should be done and how often. The variables that are most likely to be monitored are: • air pressure difference • This might be necessary in high quality cleanrooms such as ISO Class 4, and better. • airborne particle count • This might be necessary in high quality cleanrooms such as ISO Class 4, and better. • where appropriate, microbiological counts.

14. 10. Measurement of Air Quantities and Pressure Differences

15. Purpose • A cleanroom must have sufficient clean air supplied to dilute and remove the airborne contamination generated within the room. • Air Cleanliness: • Turbulently ventilated cleanroom • air supply; the more air supplied in a given time, the cleaner the room. • unidirectional cleanroom • air supply velocity • Test: • Initial testing of the design • Regular intervals check

16. Air Quantities • Instruments: • Hoods: air supply volumes • Anemometers: air velocities • Turbulently ventilated rooms • measured within the air conditioning ducts Pitot-static tube

17. Measuring air quantities from within a cleanroom • Air air filter (no diffuser) anemometer at the filter face average velocity  air volume • Difficulty: the non-uniformity of the air velocity inaccurate measurement • Air air diffusers unevenness of air velocities incorrect air volume • Hood: air supply volume average velocity measured at the exit of the hood air volume

18. Anemometers • Anemometers: away from the filter of about 30cm (12 inches) • Vane Anemometer • Principle: Air supply  turning a vane  frequency  velocity • Accuracy: velocity is less than about 0.2 m/s (40 ft/min), the mechanical friction affects the turning of the vane

19. Vane Anemometer

20. Thermal Anemometers • Principle: Air passing through the head of the instrument cooling effect  the air velocity: Fig.10.3 : a bead thermistor (有孔的電熱調節器) • Low velocities can be measured with this type of apparatus

21. Differential Pressure Tests • The units: • Pascals, inch water gauge are used (12Pa = 0.05 inch water gauge). • Pressure difference: 10 or 15 Pa between clean areas • 15 Pa is commonly used between a cleanroom and an unclassified room, • 10 Pa between two cleanrooms.

22. Large openings: • problems can occur when trying to achieve a pressure difference between areas connected by large openings, such as a supply tunnel. To achieve the suggested pressure drop : • Very large air quantities through the tunnel • To accept a lower pressure difference

23. Apparatus for measuring pressure differences • Manometer: • range of pressure difference of 0-60 Pa (0-0.25 inch water) • inclined manometer; magnehelic gauge; electronic manometer

24. Inclined manometer • works by pressure pushing a liquid up an inclined tube. • small pressure changes in the inclined tube up to a pressure of about 60 Pa. • After that pressure, the tube moves round to the vertical measuring pressure differences can be in the 100 to 500 Pa range.

25. Methods of checking pressure differences • pressure differences between areas • adjusting the pressure differences : • extract be reduced to increase the pressure, and increased to decrease it. • If manometers are not permanently installed, a tube from a pressure gauge is passed under the door, or through an open by-pass grille or damper into the adjacent area. • In some ventilation systems, the pressures within rooms are measured with respect to one reference point. When this type of system is being checked, the pressure difference across a doorway can be calculated by subtracting the two readings of the adjoining spaces.

27. 11. Air Movement Control Between and Within Cleanrooms

28. Purposes • To show that a cleanroom is working correctly, it is necessary to demonstrate that no contamination infiltrates into the cleanroom from dirtier adjacent areas. • Cleanroom Containment Leak Testing • Airborne contamination: doors and hatches, holes and cracks in the walls, ceilings and other parts of the cleanroom fabric

29. Contamination can be pushed into the cleanroom at • ceiling-to-wall interface • filter and lighting housings-to-ceiling interfaces • ceiling-to-column interface • the cladding of the ceiling support pillars • Service plenums and the entry of services into the cleanroom: electrical sockets and switches, and other types of services providers. Particularly difficult to foresee and control in a negatively pressurized containment room.

31. Methods of checking infiltration • Smoke test (dust test) • flow direction: open door, or through the cracks around a closed door, cracks at the walls, ceiling, floor and filter housings, service ducts or conduits. • Difficulty • where the containment originates from may be unknown, and it is often difficult to find the places to release test smoke.

32. Containment leak testing • Timing • handing it over to the user • major reconstruction work has been carried out • ISO 14644-2 lists the ‘containment leak’ test as an ‘optional’ test and suggest a re-testing interval of two years

33. Air Movement Control within a Cleanroom • sufficient air movement • dilute, or remove airborne contamination prevent a build-up of contamination • turbulently ventilated cleanroom: • good mixing, critical areas: where the product is exposed to the risk of contamination • unidirectional flow cleanroom • critical areas should be supplied with air coming directly from the high efficiency filters. However, problems may be encountered because of: • heat rising from the machinery and disrupting the airflow • obstructions preventing the supply air getting to the critical area • obstructions, or the machinery shape, turning the unidirectional flow into turbulent flow • contamination being entrained into the clean air.

34. Air movement visualization • Objective: sufficient clean air gets to the critical areas qualitative methods • Visualization: • Streamers • smoke or particle streams • Streamers (threads or tapes): • high surface-area-to-weight ratio, ex. recording tapes • A horizontal flow: 0.5 m/s (100 ft/min) streamer 45° to the horizontal • about 1m/s (200 ft/min) almost horizontal.

35. Streamers

36. smoke or particle streams • oil smoke  contamination • Water vapour : from solid C02 (dry ice) or by nebulizing water

37. putter and smoke tube': • Titanium tetrachloride (TiCl4)produces acid  corrodes some surfaces harmful to sensitive machinery or harm the operator's lungs.

38. Air Movement in turbulently ventilated rooms • working well: quickly dispersed • not working well Areas: not disperse quickly contamination build up  improved by adjusting the air supply diffuser blades, removing an obstruction, moving a machine.

39. Air Movement in unidirectional flow • air moves in lines • Visualisation techniques: smoke stream • Still picture

40. Air velocity and Direction measurement • A permanent record: velocity and direction

42. Recovery Test Method • A quantitative approach • A burst of test particles introduced into the area to be tested mixed with their surroundingsthe airborne particle count should be measured, • A useful endpoint is one-hundredth of the original concentration, and the time taken to reach there can be used as an index of efficiency.

44. Ch. 12 Filter Installation Leak Testing

45. HEPA test • Manufacturer's factory and packed OK • Unpacked and fitted into the filter housings maybe damage • Leakage problems • casing • housing • Testing : artificial test aerosol

46. Leakage areas in a HEPA filter A - filter paper-to-case cement area C- gasket D - frame joints. B - filter paper (often at the paper fold)

47. Gasket and casing leaks from filter inserted up from cleanroom Gasket leaks from filters inserted down from ceiling

48. Figure 12.4 Filter-housing gel seal method

49. Artificial Smoke and Particle Test • Cold-generated oils • Di-octyl phthalate (DOP)鄰苯二甲酸二辛酯 • oily liquid, potentially toxic effects, no longer used • Di-octylsebacate (DOS)葵二酸二辛酯 • 常用 • poly alpha olefin (PAO)聚烯茎油 • 常用

50. Cold-generated oil Test Air+ oil particle Laskin nozzle air (high pressure) 0.5mm Air pump oil