ASTM F91-06(2011)

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Designation: F91 − 06 (Reapproved 2011)
Standard Practice for
Testing for Leaks in the Filters Associated With Laminar
Flow Clean Rooms and Clean Work Stations by Use of a
Condensation Nuclei Detector
This standard is issued under the fixed designation F91; the number immediately following the designation indicates the year of original
adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.Asuperscript
epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3. Summary of Practice
3.1 This recommended practice takes advantage of the fact
1.1 This practice covers the testing of the integrity of
that a HEPAfilter retains a high percentage of the condensation
high-efficiency particulate air (HEPA) filters installed in lami-
nuclei found in ordinary room air. In this recommended
nar flow clean rooms of the ceiling to floor or wall to wall type,
practice a nuclei counting apparatus is arranged to sample
and laminar flow clean work stations. The recommended
small areas at the filter surface and the joints at the filter edges.
practice may be used to detect faults or voids in the filter media
The HEPA filter effluent normally shows a low nuclei count
itself or in the joints between the filter and the room or work
(<100 particles/cm ).When a leaking filter area is encountered,
station structure. The determination of filter media efficiency is
an increase of at least ten-fold in the particle count is noticed
not within the scope of this practice.
within the 2-s response time of the nuclei counter.
1.2 The values stated in SI units are to be regarded as
standard. No other units of measurement are included in this
4. Apparatus
standard.
2,3
4.1 Condensation Nuclei Counter.
1.2.1 Exception—The values given in parentheses in inch-
4.2 Plastic Tubing , 9.5 mm ( ⁄8 in.) in outside diameter; 6.5
pound units are for information only.
mm ( ⁄4 in.) in inside diameter; of suitable length, not to exceed
1.3 This standard does not purport to address all of the
1.5 m (5 ft).
safety concerns associated with its use. It is the responsibility
4.3 Glass Laboratory Funnel, 50 mm in outside diameter, 7
of the user of this standard to establish appropriate safety and
mm in stem diameter, 80 mm over-all length.
health practices and determine the applicability of regulatory
limitations prior to use.
4.4 Double-Pole Single-Throw Relay, 115 V, 8 A.
5. Preparation for Test
2. Terminology
5.1 Assemble the apparatus by slipping one end of the
2.1 Definitions:
plastic hose over the funnel stem, and the other end over the
2.1.1 condensation nuclei—particles within the size range
nuclei counter input nipple.
from 0.001 to 0.1-µm radius.
5.2 Turn on the electrical supply to the nuclei counter and
2.1.2 HEPA filter—high-efficiency particulate air filter.
allow 30 min warm up time with the input tube sampling the
2.1.3 laminar flow—airflow in which the air confined within
effluent from a HEPA filter.
the walls of a room or a smaller work station moves as an
5.3 Measure the nuclei concentration at the intake to the
isovelocity front along parallel flow lines.
HEPA filter. A concentration of less than 1000 particles/cm
2.1.4 leak—a gap or void in the filter media, or in the
indicatesaconcentrationinsufficientforconvenientlydetecting
associated gaskets, which permits unfiltered room air to pen-
leaks in the filter or its gaskets.
etrate the clean room or clean work station.
5.3.1 In the event that a nuclei concentration of less than
1000 particles/cm occurs when sampling a clean work station,
This practice is under the jurisdiction of ASTM Committee E21 on Space
Simulation andApplications of Space Technology and is the direct responsibility of Rich,T.A., “AContinuous Recorder for Condensation Nuclei,” Geofisica Pura
Subcommittee E21.05 on Contamination. e Applicata, Milano, Vol. 50, 1961, III, pp. 46–52.
Current edition approved Sept. 1, 2011. Published February 2012. Originally General Electric Co., Schenectady, NY, Model No. 112L482G1 has been found
approved in 1968. Last previous edition approved in 2006 as F91 – 06. DOI: satisfactory.
10.1520/F0091-06(2011). Tygon tubing or equivalent has been found satisfactory for this purpose.
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