ISO 17191:2004(E) 含含营 Key HEPA filter 2 cassette 3 Tygon tubing To vacuum. Figure2—Cassette-dryingunit 6 Procedure 6.1 Sample preparation and precautionary measures 6.1.1 Preparationand cleaningof cassettespriortoairmonitoring 6.1.1.1 In summary, cassettes are assembled, filters are wet with 0,5 ml IPA, washed with 0,2 % KCl solution, then rinsed with de-ionized water and dried before use as dust collection devices or blanks 6.1.1.2 Assemble the desired number of cassettes without touching with the fingers any inside surface of the cassette. Analysts may wear plastic gloves to reduce contamination. Use forceps to handle filters and backing pads. If filters or backing pads are dropped, they should be discarded. Wash any hardware before re- use if dropped. Put only the bottom-end plug in the cassette, keeping the other plugs in the plastic bag. Tape the cassette over the circumference at the joint to assure a good seal. 6.1.1.3 Add 0,5 ml of IPA to the cassette to wet the filter and fill the cassette with 0,2 % KCl. Allow the 6.1.1.4 Using vacuum suction (Figure 3), draw the solution through the cassette.Turn-off the vacuum just as the cassette empties. Do not pull air through the cassette after the solution has been drawn out. Fill the cassette with deionized water and pull through to rinse the cassette. Repeat this three more times. @ ISO 2004 All rights reserved nal Organization for Standardization Not for Resale ISO17191:2004(E) Key Tygon tubing 1 Put cassette here. To vacuum. Figure3—Vacuumwashingstand 6.1.1.5 After the last rinse, connect the inlet of the cassette to an HEPA (High Efficiency Particulate-free Air) filter with retains particles and aerosols with diameters in excess of o,3 μm. For efficiency, up to six through the cassette for drying. The required time will vary for each cassette, but experience has shown that all visible water is removed after 2 h if the air flow rate is 0,85 I/min for each cassette. Excess drying is not when dry, and all water droplets will be evaporated from the interior of the cassettes. 6.1.1.6 Fit the inlet and outlet plugs in the cassette with forceps; do not touch the plugs with the fingers. Tighten the plugs by turning and pressing by hand. Re-inspect the cassettes after 12 h for signs of moisture. If moisture is seen, dry for as short time as possible (as in 6.1.1.5) to remove the moisture. If a cleaned cassette is accidentally opened, it should be recleaned before use. 6.1.1.7 Before releasing cleaned cassettes for air sampling, each shall be clearly labelled with a unique identification so that its preparation date can be traced. In addition, 10 % of the cassettes shall be tested for release. Keep records of the absorbance values of the water used for rinsing, and the values from the sodium determinationforthe 10%blankcassettesthatweretested. 5 CopyrahtIntematlinal organizaion ftr standardzalonghts reserved Not for Resale ISO 17191:2004(E) 6.1.1.8 In addition to the cassettes that are tested for release, five of the remaining clean cassettes should be retained for blank determinations. These are for determining the limit of detection for the test at the cassettesaresenttomorethanonelocation,thenfiveblanksshall bekeptforeachlocationinvolved.Ifanyof these blank cassettes are not used during testing, they may be made part of another batch of cassettes and carried along through the cleaning procedure. 6.1.2Preparationofcassettesforsodiumanalysisafterairmonitoring 6.1.2.1 Note that it is very important to use the same chemicals and solutions for preparing the calibration curve,andanalysisofcorrespondingsamplesandblanks.Ifallthetestsamples cannotbeprocessedwiththe same batch of solutions, run a new calibration curve with newly prepared solutions for the remaining samples and treat the results of these samples as if they are an independent series. 6.1.2.2 Take appropriate care to avoid contaminating the cassettes. Assume that fingers, work bench surfaces, the laboratory floor, etc. are c