1、Institute of Environmental Sciences and Technology IEST-RP-CC002.4 Contamination Control Division Recommended Practice 002.4 Unidirectional-Flow, Clean-Air Devices Arlington Place One 2340 S. Arlington Heights Road, Suite 620 Arlington Heights, IL 60005-4510 Phone: (847) 981-0100 Fax: (847) 981-4130
2、 E-mail: informationiest.org Web: www.iest.org IEST-RP-CC002.4 Institute of Environmental Sciences and Technology IEST 2016 All rights reserved 2 This Recommended Practice was prepared by and is under the jurisdiction of Working Group 2 of the IEST Contamination Control Division (WG-CC002). The foll
3、owing WG voting members contributed to the development of this edition of this Recommended Practice: R. Vijayakumar, WG-CC002 Chair, AERFIL Daniel Dennison, NNE Pharmaplan, Inc. Keith Flyzik, Micro-Clean, Inc. Donna Kasper, Hollingsworth CAS# 117-81-7. DOS or DEHS Dioctyl sebacate (DOS) or di(2-ethy
4、lhexyl) sebacate (DEHS); CAS# 122-62-3. HEPA (high-efficiency particulate air) filter An extended-medium, dry-type filter in a rigid frame having a minimum particle collection efficiency of 99.97% for 0.3-m mass median diameter particles of DOP when tested at rated airflow in accordance with MIL-STD
5、-282. NOTE: The foregoing is the traditional definition for the HEPA filter. Changes in filter manufacture, end-user re-quirements, and testing have introduced products that vary parametrically from filters that have been considered standard according to this definition. Additional information on th
6、is topic is given in IEST-RP-CC001. microspheres (or PSL) Monodisperse or polydisperse sized particles usually made of polystyrene latex (PSL). Monodisperse particle size is traceable to the National Institute of Standards and Technology (NIST) or other national standards bodies with re-spect to the
7、 diameter. NOTE: PSL refers to a common type of highly uniform spheres, or a suspension thereof, used to generate a solid aerosol. PSL is useful for leak testing filters where other aerosols may contaminate the filters in an unacceptable manner. The term latex refers to an emulsion in water of finel
8、y divided particles of synthetic rubber, plastic, or other elastomer, and is not to be confused with natural rubber latex. PAO (4 cSt poly-alpha-olefin) A grade of PAO with a viscosity of 4 centistokes at 100 C. With reference to filter testing, PAO also refers to a poly disperse aerosol of the desc
9、ribed material. PSL (see microspheres) ULPA (ultra-low-penetration air) filter A throwaway, extended-medium, dry-type filter in a rigid frame, having a minimum particle-collection efficiency of 99.999% (that is, a maximum particle penetration of 0.001%) when tested in accordance with the methods of
10、IEST-RP-CC007. ULPA filters are defined and described in IEST-RP-CC001. IEST-RP-CC002.4 Institute of Environmental Sciences and Technology IEST 2016 All rights reserved 10 unidirectional airflow (unidirectional flow) Air flowing in a single direction at the work zone of a clean-air device or clean a
11、rea. This can be verified by the absence of recirculating or stagnant air at the work zone either by visual methods or other techniques. Formerly referred to as laminar airflow. unidirectional clean air Unidirectional airflow that has been filtered with at least a Type C or more efficient filter. wo
12、rk zone The volume within the clean-air device or cleanroom that is designated for clean work and for which testing is re-quired. The work zone volume is defined by an entrance plane and an exit plane (normal to the airflow where there is unidirectional airflow). 4 BACKGROUND AND PURPOSE This RP pro
13、vides a set of recommended test procedures for determining clean-air-device performance. The principal purpose of clean-air-device performance testing is classification of air cleanliness in accordance with ISO 14644-1. Additional tests, such as those related to airflow characteristics, sources of p
14、articles, device pressurization and integ-rity, and environmental issues, provide a more complete characterization of performance of the device. When purchasing a clean-air device, appropriate sections of this RP should be referenced in the purchase order to define the expected performance of the un
15、it as received. 4.1 Applications Unidirectional-flow, clean-air devices are designed to provide a localized (stand-alone) clean environment for pro-tecting a product or manufacturing operation. Historically, these devices have been utilized in product manufactur-ing, sterility testing, or compoundin
16、g sterile preparations. These devices may be used within uncontrolled environments or surrounded by another controlled environment of lesser cleanliness. As with any device, all unidirectional-flow, clean-air devices should be used properly and be certified after installa-tion and at routine interva
17、ls to verify that the design requirements are being maintained. Whenever unidirectional airflow is considered, care should be exercised to avoid obstructions between the clean-air source and the critical work area that may cause turbulence or interfere with the desired environment within the clean z
18、one, as well as obstructions (including personnel) downstream from the product that can back stream contam-inants onto the product. In selecting the airflow pattern, horizontal or vertical, the user should consider the equipment and process to be used in the device with relationship to airflow. Many
19、 of these units can be modified to accommodate accessories such as sinks, utilities, and special process equip-ment. To define what is expected from the supplier, a drawing should be included with the request for quotation and with the purchase order. It should be noted that the placement of items w
20、ithin or on the work surface can alter the airflow patterns within the device and reduce its effectiveness unless the appropriate steps are taken during the orig-inal design and fabrication. 4.2 Operational concerns Exhausting clean-air devices should be equipped with a flow sensor to monitor supply
21、 and exhaust air. These devic-es are effective only if the air balance is correct. If the air balance drifts outside of the specifications, either the product may become contaminated or the operator may be exposed to potentially harmful materials. Air balance is of interest generally for biological
22、safety and containment cabinets. Procedures for air balance can be found in the instructions provided by the cabinet manufacturer or in NSF/ANSI Standard 49 and are not included in this RP. Fur-ther guidance on exhaust and proper ventilation systems may be found in ANSI/AIHA Z9.5 and ANSI/AIHA Z9.7.
23、 Whenever a fan-filter unit (see 5.9) or clean-air module (see 5.10) is used to provide a localized clean area, enclo-sure of the airflow is necessary to maintain the unidirectional flow from the filter to the critical work area. If the IEST-RP-CC002.4 Institute of Environmental Sciences and Technol
24、ogy IEST 2016 All rights reserved 11 airflow is not enclosed, the clean-air zone may be compromised by room air currents, cross-drafts, or induced air contaminants drawn into the HEPA-filtered airstream. Additional information concerning installation and maintenance is provided in Appendixes A, B, C
25、, and D. 5 TYPES OF DEVICES This section describes common types of unidirectional-flow, clean-air devices. The descriptions and figures provid-ed are generic in nature and do not represent all possible variations. Detailed drawings and specifications should be included in the customer-supplier agree
26、ment. 5.1 Horizontal flow A horizontal-flow device (see Figure 1) has a solid or perforated work surface, enclosed on the top and sides of the clean zone, with HEPA or ULPA filter(s) behind the clean zone. In console models, the motor-blower is typically mounted below and behind the work surface. In
27、 benchtop models, the motor-blower is mounted above and behind the HEPA or ULPA filter(s). The air flows horizontally through the clean zone and out into the surrounding area. Figure 1Horizontal-flow device (bench or tabletop). IEST-RP-CC002.4 Institute of Environmental Sciences and Technology IEST
28、2016 All rights reserved 12 5.2 Horizontal flow with exhaust A horizontal-flow device with exhaust (see Figure 2) has a solid or perforated work surface, enclosed on the top, rear, and sides of the clean zone. HEPA or ULPA filter(s) behind the clean zone provide filtered air across the prod-uct or p
29、rocess, pulling process-generated airborne particles and other contaminants into the air intake on the front edge of the workbench. The air intake reduces personnel exposure to contaminants escaping from the product or process, while providing product and cross-contamination protection. Figure 2Hori
30、zontal-flow device with exhaust (console). IEST-RP-CC002.4 Institute of Environmental Sciences and Technology IEST 2016 All rights reserved 13 5.3 Horizontal flow with recirculation A horizontal-flow device with recirculation (see Figure 3) has a solid or perforated work surface, enclosed on the top
31、, rear, and sides of the clean zone, with HEPA or ULPA filter(s) behind the clean zone. In console models, the motor-blower is typically mounted below and behind the work surface. In benchtop models, the motor-blower is mounted above and behind the HEPA or ULPA filter(s). The air flows horizontally
32、through the clean zone and out into the surrounding area. The bench sidewalls or work surface edge, or both, may be designed with high-speed re-turn air slots that provide clean air recirculation and prevent particle back streaming from the room environment. Figure 3Horizontal-flow device with recir
33、culation (console). IEST-RP-CC002.4 Institute of Environmental Sciences and Technology IEST 2016 All rights reserved 14 5.4 Vertical flow A vertical-flow device (see Figure 4) has a solid or perforated work surface, enclosed on the rear and sides of the clean zone, with a motor-blower and HEPA or UL
34、PA filter(s) above the clean zone. The air flows down over the partially enclosed clean zone and out into the surrounding area. The size of the front opening may be controlled with a fixed, sliding, or hinged transparent sash or viewscreen. This device can be used to provide a clean environment for
35、many operations that do not generate materials that may be hazardous or harmful to the operator, process, or environment. Figure 4Vertical-flow device (console). IEST-RP-CC002.4 Institute of Environmental Sciences and Technology IEST 2016 All rights reserved 15 5.5 Vertical flow with recirculation A
36、 vertical-flow device with recirculation (see Figure 5) is similar to the vertical device except the supplied clean air returns to the fan in the device through a perforated horizontal work surface or return-air openings at the front or rear of the work surface, or both. The motor-blower is typicall
37、y located above the work surface. Figure 5Vertical-flow device with recirculation (bench or tabletop). IEST-RP-CC002.4 Institute of Environmental Sciences and Technology IEST 2016 All rights reserved 16 5.6 Vertical flow with exhaust A vertical-flow device with exhaust (see Figure 6) is similar to a
38、 recirculating vertical device except: a) Air is drawn through an air-inlet grille on the suction side of the fan and passes through the front clean zone and downward through a perforated work surface. The volume of intake air is balanced with the volume of air exhausted and the volume of air suppli
39、ed by the motor-blower of the device. The volume of air exhausted should be greater than the volume of air supplied by the motor-blower. b) All the air drawn down through the returns in the work surface is exhausted outside the work area and usually outside the building after being properly treated,
40、 when necessary, to remove any harmful materials, heat loads, or nuisance odors. c) The supply air motor-blower is typically mounted above the clean zone inside the device. d) The exhaust airflow may be controlled by a remote-location roof blower, exhaust-air-handling filter bank, or an exhaust blow
41、er installed at the unidirectional-flow, clean-air device. e) In applications involving the discharge of hazardous or volatile materials, vapors, aerosols, or gases, the exhaust ductwork should be operated under negative pressure, i.e., the exhaust blower should be the final component of the exhaust
42、 system. Further guidance is provided in ANSI/AIHA Z9.7. Figure 6Vertical-flow device with exhaust (bench or tabletop). IEST-RP-CC002.4 Institute of Environmental Sciences and Technology IEST 2016 All rights reserved 17 5.7 Vertical flow, dual access The vertical-flow device has a solid or perforate
43、d work surface, and front and rear access to the clean work zone (see Figure 7), with a motor-blower and HEPA or ULPA filter(s) above the clean zone. The air flows downward through the partially enclosed clean zone and out into the surrounding area. Alternative configurations may place the motor-blo
44、wer and HEPA or ULPA filter(s) under the work surface where the filtered air is sent back to the top of the unit for recirculation as unidirectional HEPA- or ULPA-filtered downflow air. The size of the front opening may be con-trolled with a fixed, sliding, or hinged transparent sash or viewscreen.
45、This device can be used to provide a clean environment for many operations that do not generate materials that may be hazardous or harmful to the operator, process, or environment. Figure 7Vertical-flow, dual-access device. IEST-RP-CC002.4 Institute of Environmental Sciences and Technology IEST 2016
46、 All rights reserved 18 5.8 Vertical flow, dual access, with exhaust The vertical-flow device has a solid or perforated work surface, and front and rear access to the clean work zone (see Figure 8), with a motor-blower and HEPA or ULPA filter(s) above the clean zone. The air flows downward through t
47、he partially enclosed clean zone and is drawn through work surface intake grilles by use of a second blower with HEPA- or ULPA-filter protection. The lower exhaust blower may provide a containment air curtain. The filtered exhaust air may be discharged back into the room or recirculated back to the
48、top supply blower. The size of the front opening may be controlled with a fixed, sliding, or hinged transparent sash or viewscreen. This device can be used to provide a clean environment for many operations that may generate nuisance contaminants (e.g., particles, animal dander). Figure 8Vertical-fl
49、ow, dual-access device with exhaust. IEST-RP-CC002.4 Institute of Environmental Sciences and Technology IEST 2016 All rights reserved 19 5.9 Fan-filter unit Fan-filter units (see Figure 9) are clean-air devices that incorporate a single HEPA or ULPA filter and attached ple-num with a motor-blower to draw in air and force the air through the filter. The unit is typically designed for verti-cal-flow, lay-in installation into a suspended ceiling grid or may be part of a portable vertical or horizontal clean-air device. Although originally designed to be comple
