1、Designation: D 6329 98 (Reapproved 2008)Standard Guide forDeveloping Methodology for Evaluating the Ability of IndoorMaterials to Support Microbial Growth Using StaticEnvironmental Chambers1This standard is issued under the fixed designation D 6329; the number immediately following the designation i
2、ndicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 Many different types of microorganisms
3、(for example,bacteria, fungi, viruses, algae) can occupy indoor spaces.Materials that support microbial growth are potential indoorsources of biocontaminants (for example, spores and toxins)that can become airborne indoor biopollutants. This guidedescribes a simple, relatively cost effective approac
4、h to evalu-ating the ability of a variety of materials to support microbialgrowth using a small chamber method.1.2 This guide is intended to assist groups in the develop-ment of specific test methods for a definite material or groupsof materials.1.3 Static chambers have certain limitations. Usually,
5、 onlysmall samples of indoor materials can be evaluated. Care mustbe taken that these samples are representative of the materialsbeing tested so that a true evaluation of the material isperformed.1.4 Static chambers provide controlled laboratory microen-vironment conditions. These chambers are not i
6、ntended toduplicate room conditions, and care must be taken wheninterpreting the results. Static chambers are not a substitute fordynamic chambers or field studies.1.5 A variety of microorganisms, specifically bacteria andfungi, can be evaluated using these chambers. This guide is notintended to pro
7、vide human health effect data. However, organ-isms of clinical interest, such as those described as potentiallyallergenic, may be studied using this approach.1.6 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user
8、of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 1193 Specification for Reagent WaterD 1356 Terminology Relating to Sampling and Analysis ofAtmospheresE 104 Prac
9、tice for Maintaining Constant Relative Humidityby Means of Aqueous Solutions2.2 APHA Standards3:Standard Methods for the Examination of Water and Waste-water3. Terminology3.1 DefinitionsFor definitions of terms used in this guide,refer to Terminology D 1356.3.2 Definitions of Terms Specific to This
10、Standard:3.2.1 amplificationthe act or result of increasing thequantity of microorganisms.3.2.2 CFUcolony forming unit, which may arise from asingle organism or multiple units, such as spores, in the case ofthe fungi.3.2.3 colonymacroscopically visible growth.3.2.4 inoculationthe act of introducing
11、a microorganism(inoculum) into the test material.3.2.5 inoculumviable test microorganism introduced ontoa material by implanting a small amount on the surface orsubstrate.3.2.6 platepetri dish containing microbiological agar me-dia on which microorganism are grown.3.2.7 static chambera small chamber
12、 (enclosed space)with no internal forced air motion.3.2.8 susceptibilitythe vulnerability of a material or sur-face to colonization by microorganisms.4. Significance and Use4.1 The static chambers have several different applications:1This guide is under the jurisdiction of ASTM Committee D22 on Air
13、Qualityand is the direct responsibility of Subcommittee D22.05 on Indoor Air.Current edition approved April 1, 2008. Published July 2008. Originallyapproved in 1998. Last previous edition approved in 2003 as D 6329 - 98(2003).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orco
14、ntact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from American Public Health Association, 1015 15thSt., NW,Washington, DC 20036.1Copyright ASTM International, 100 Barr Harbo
15、r Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4.1.1 The static chambers can be used to compare thesusceptibility of different materials to the colonization andamplification of various microorganisms under defined condi-tions.4.1.2 Chambers operated at high relative humidities
16、 may beused to perform worst case scenario screening tests on mate-rials by providing an atmosphere where environmental condi-tions may be favorable for microbial growth.4.1.3 Use of multiple chambers with different environmen-tal parameters, such as a range of relative humidities, permitsthe evalua
17、tion of multiple microenvironments and allowsinvestigation of materials under differing environmental con-ditions.4.1.4 Drying requirements for wetted materials may also beinvestigated. This information may be relevant for determiningmaterial resistance to microbial growth after becoming wet.These c
18、onditions may simulate those where materials aresubjected to water incursion through leaks as well as duringremediation of a building after a fire.4.1.5 Growth rates of microorganisms on the material mayalso be investigated. Once it has been established that organ-isms are able to grow on a particul
19、ar material under definedconditions, investigations into the rate of organism growth maybe performed. These evaluations provide base line informationand can be used to evaluate methods to limit or containamplification of microorganisms.4.2 These techniques should be performed by personnelwith traini
20、ng in microbiology. The individual must be compe-tent in the use of sterile technique, which is critical to excludeexternal contamination of materials.5. Apparatus5.1 Static ChamberChambers should be relatively smalland portable, contain three or four shelves, and be easilydecontaminated. In additio
21、n, transparent walls are desirablebecause visual inspection of the test material and monitoring ofinstruments (that is, hygrometers) without opening the cham-ber is preferred. Fig. 1 is a schematic diagram of a possiblestatic chamber. Acrylic desiccators are readily available, easilyadaptable, and r
22、elatively inexpensive. Other options, such asglass, are also acceptable. Glass has the advantage of beingautoclavable; however, it is frequently much less portable. Thechamber door must provide ready access to the materials butshould be airtight when closed.5.1.1 Relative HumidityMaintain humidities
23、 through theuse of saturated salt solutions contained in trays on the bottomof the chambers (see Practice E 104). It is essential that thechambers be tightly sealed so that the desired humidity will bemaintained. Place hygrometers in the chambers for confirma-tion that humidities are being maintaine
24、d, although saturatedsalt solutions are themselves standards. Exercise care that thesalts selected for use in the chamber are not inhibitory to thetest organisms.5.1.2 TemperatureControl the temperature of the cham-bers. The chambers may be externally controlled through theuse of constant temperatur
25、e environments, such as a room orincubator. Chart recorders or other data logging devices arerecommended to confirm maintenance of temperature. Con-trolled temperature is critical for two reasons. First, it can havea profound effect on the growth of microorganisms. Second,relative humidity is depend
26、ent upon temperature. The controllimits may be defined by consulting a psychometric chart anddetermining the impact of temperature on a specific test RH.5.1.3 Characterize instrumentation for evaluating other pa-rameters if the instruments are to be employed during materialtesting. Conditions such a
27、s light need to be noted and con-trolled during the course of an experiment as these conditionsmay have an effect on the growth of the test organism. Lightmay be controlled externally by placing the chambers in adarkened room to remove light or in a continuously lightedroom for a constant light sour
28、ce.5.2 Provide ports, where needed, for the insertion of probesto monitor and record temperature and relative humidity, usingexternally located instrumentation as long as it is well sealedand contamination is avoided.5.3 DecontaminationDecontaminate the chamber beforeinitiating any analysis. Surface
29、 disinfection or vapor phasedisinfection may be appropriate. Glass may be autoclaved.Follow the manufacturers instructions, especially any safetyprecautions. If a chemical disinfectant is employed, clear thechambers of any residual disinfectant to prevent interferencewith the growth of the microorga
30、nisms on the material beingevaluated. Thoroughly ventilate the chambers in a cleanenvironment. Decontaminate the salt solutions. The methodused is dependent upon the composition of the salts selected.Any instrumentation to be used during the evaluations, such ashygrometers, may be removed from the c
31、hambers during thedecontamination procedure of the chamber surfaces and de-contaminated separately; however, it is generally more effec-tive for them to remain in the chambers. Verify the efficacy ofthe decontamination procedure as part of the QualityAssurance/Quality Control (QA/QC) plan.5.4 Decont
32、aminate the work area around the chambersroutinely, especially before opening the chamber door. Thechambers should be kept in a clean room, functionally Class100 000 (M 6.5 or ISO 8) or better.6. Reagents6.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indica
33、ted, it is intended thatall reagents conform to the specifications of the Committee onAnalytical Reagents of the American Chemical Society whereFIG. 1 Schematic of Example Static ChamberD 6329 98 (2008)2such specifications are available.4Other grades may be used,provided it is first ascertained that
34、 the reagent is of sufficientlyhigh purity to permit its use without lessening the accuracy ofthe determination.6.2 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean reagent water as certifiedby Type II of Specification D 1193. It should conform to theType A s
35、pecifications for microbial classification.6.3 Microbiological MediaChoose appropriate media de-pending upon the test microorganism selected. Commerciallyprepared media may be acceptable, but it may be necessary toprepare organism specific media. References should be con-sulted to determine the prop
36、er media for optimal growth of thetest organism.7. Characterization of Static Chamber7.1 Characterize static chambers for all environmental pa-rameters being measured before any material evaluations areperformed. Chambers should be characterized for at leastrelative humidity and temperature. Take su
37、fficient readings toensure that the conditions will be maintained throughout thecourse of the experiment and will meet the QA/QC standardsdeveloped for a specific test.7.1.1 EquilibrationEquilibrate disinfected chambers con-taining hygrometers before taking the first relative humidityreading. Place
38、the hygrometers on a shelf for ease of readingthrough the walls of the chamber without opening the door.Take multiple sequential readings at appropriate intervals thatwere determined experimentally. The variation of the instru-mentation must be determined and taken into consideration.For example, a
39、minimum of four similar readings (65 %) overan 8 h period may be determined to demonstrate equilibrium.7.1.2 RecoveryDetermine the amount of time required forthe chamber relative humidity to recover to test levels afteropening the door for 1 to 2 min. This determination may becrucial, especially at
40、the higher relative humidities. Exercisecare to utilize hygrometers that have a rapid response time.7.2 Check chamber relative humidity daily, and recordreadings depending on test length.8. Sample Preparation8.1 Specific details on the preparation of the samples willdepend upon the characteristics o
41、f the material to be tested.Generally, replicate small pieces of the test material should beused. Depending upon the material, pieces as small as 4 by 4cm may be used. Pieces should be placed on sterile petri dishesor other appropriate holders on the shelves in the chamber.Include controls and blank
42、s within the QA/QC framework.8.2 Common microbiological practice is to sterilize a sur-face or material before inoculation to ensure that the testorganism is the only source being evaluated. Autoclaving is anextremely effective method if such a procedure does not alterthe test material. Other method
43、s, such as ionizing and non-ionizing irradiation, ultraviolet, dry heat, and surface or vaporphase disinfection, are also acceptable if these methods do notharm the material and do not have residue effects or if all tracesof the disinfectant can be removed prior to testing. Consult thetest material
44、manufacturer or conduct tests with the testmaterial to determine the best method of sterilization. Specificdetails for decontamination depend upon the method selectedand should be worked out before actual testing begins withinthe QA/QC framework.8.3 Equilibrate or bring to near equilibrium samples i
45、n thechamber before inoculation with the test organism. Equilibra-tion time will depend upon both the material to be tested andthe chamber relative humidity selected for the test. Determineequilibration times for each material prior to testing.8.3.1 Ascertain equilibration by determining when the bu
46、lkmoisture content of the material reaches a constant value. Theuse of a calibrated analytical balance is recommended.8.3.2 Compute the bulk moisture content of the test materialas follows:MC 5 Mb Md! / Md# 3 100 (1)where:MC = bulk moisture content (%),Mb= mass of the small piece (g), andMd= mass of
47、 the small piece after drying (g).Mdmay be determined either by oven drying at 105 to 110Cor desiccation to constant weight depending upon the testmaterial. Time required for drying is determined experimen-tally. A sample can be considered dry when no significantweight change is detected in two cons
48、ecutive weighings at least1 h apart.9. Selection of Test Organism9.1 Selection of the appropriate test organisms is extremelyimportant. Since growth requirements vary for different organ-isms, the selection process should include a justification for theparticular organism or organisms chosen. Testin
49、g of materialswith many different organisms from diverse groups is optimal.At a minimum, representative bacteria and fungi should bothbe tested. Initial tests should be performed with only onespecies of microorganism.9.1.1 Criteria for organism selection are based on a numberof factors.Appropriateness of the organism for the test materialand the environment where the material is used are key factors.9.1.2 Literature reviews or reference articles reporting onindoor field investigations are good sources of suggestions forpotential test organisms.9.2 Documentation
