ASTM_F_91_-_06_2011.pdf

Designation:F9106(Reapproved 2011)Standard Practice forTesting for Leaks in the Filters Associated With LaminarFlow Clean Rooms and Clean Work Stations by Use of aCondensation Nuclei Detector1This standard is issued under the fixed designation F91;the number immediately following the designation indicates the year of originaladoption or,in the case of revision,the year of last revision.Anumber in parentheses indicates the year of last reapproval.Asuperscriptepsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This practice covers the testing of the integrity ofhigh-efficiency particulate air(HEPA)filters installed in lami-nar flow clean rooms of the ceiling to floor or wall to wall type,and laminar flow clean work stations.The recommendedpractice may be used to detect faults or voids in the filter mediaitself or in the joints between the filter and the room or workstation structure.The determination of filter media efficiency isnot within the scope of this practice.1.2 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.2.1 ExceptionThe values given in parentheses in inch-pound units are for information only.1.3 This standard does not purport to address all of thesafety concerns associated with its use.It is the responsibilityof the user of this standard to establish appropriate safety andhealth practices and determine the applicability of regulatorylimitations prior to use.2.Terminology2.1 Definitions:2.1.1 condensation nucleiparticles within the size rangefrom 0.001 to 0.1-m radius.2.1.2 HEPA filterhigh-efficiency particulate air filter.2.1.3 laminar flowairflow in which the air confined withinthe walls of a room or a smaller work station moves as anisovelocity front along parallel flow lines.2.1.4 leaka gap or void in the filter media,or in theassociated gaskets,which permits unfiltered room air to pen-etrate the clean room or clean work station.3.Summary of Practice3.1 This recommended practice takes advantage of the factthat a HEPAfilter retains a high percentage of the condensationnuclei found in ordinary room air.In this recommendedpractice a nuclei counting apparatus is arranged to samplesmall areas at the filter surface and the joints at the filter edges.The HEPA filter effluent normally shows a low nuclei count(100 particles/cm3).When a leaking filter area is encountered,an increase of at least ten-fold in the particle count is noticedwithin the 2-s response time of the nuclei counter.4.Apparatus4.1 Condensation Nuclei Counter.2,34.2 Plastic Tubing4,9.5 mm(38in.)in outside diameter;6.5mm(14in.)in inside diameter;of suitable length,not to exceed1.5 m(5 ft).4.3 Glass Laboratory Funnel,50 mm in outside diameter,7mm in stem diameter,80 mm over-all length.4.4 Double-Pole Single-Throw Relay,115 V,8 A.5.Preparation for Test5.1 Assemble the apparatus by slipping one end of theplastic hose over the funnel stem,and the other end over thenuclei counter input nipple.5.2 Turn on the electrical supply to the nuclei counter andallow 30 min warm up time with the input tube sampling theeffluent from a HEPA filter.5.3 Measure the nuclei concentration at the intake to theHEPA filter.A concentration of less than 1000 particles/cm3indicates a concentration insufficient for conveniently detectingleaks in the filter or its gaskets.5.3.1 In the event that a nuclei concentration of less than1000 particles/cm3occurs when sampling a clean work station,1This practice is under the jurisdiction of ASTM Committee E21 on SpaceSimulation and Applications of Space Technology and is the direct responsibility ofSubcommittee E21.05 on Contamination.Current edition approved Sept.1,2011.Published February 2012.Originallyapproved in 1968.Last previous edition approved in 2006 as F91 06.DOI:10.1520/F0091-06(2011).2Rich,T.A.,“AContinuous Recorder for Condensation Nuclei,”Geofisica Purae Applicata,Milano,Vol.50,1961,III,pp.4652.3General Electric Co.,Schenectady,NY,Model No.112L482G1 has been foundsatisfactory.4Tygon tubing or equivalent has been found satisfactory for this purpose.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 move the work station into a room having a less clean ambientsuch as a room not supplied with filtered air.5.3.2 In the event that the intake nuclei concentration of lessthan 1000 particles/cm3occurs in a laminar flow room of theceiling to floor or wall to wall type,make the filter leak test ata time when the room is operating on a full work schedule withthe maximum number of occupants.5.3.3 Should the nuclei concentration level of the input airfail to reach 1000 nuclei/cm3after executing steps 5.3.1 or5.3.2,set up a nuclei generator using a DPST relay(see 4.4).5.3.3.1 Wire one side of the relay so that in the at-restcondition current flows through the relay field coil,drawing thearmature toward the field coil pole piece.This wiring arrange-ment should