# FILTER INSTALLATION LEAK TESTS – AEROSOL PHOTOMETER

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TEST METHOD FOR CLEAN ROOMS

The photometer test method employs either logarithmic or linear mass concentration detection and does not provide discrete quantitative analysis. This test is performed by introducing DOP, PAO or another specified substitute aerosol upstream of filters and verifying the installations integrity by scanning the downstream side of the filters with the photometer and appropriate probe.

INSTRUMENTATION AND EQUIPMENT

• A thermal or laskin nozzle generator.
• Scanning probe.

TEST PROCEDURES

• Introduce the aerosol into the air supplied to the filters in a manner which will produce a uniform challenge concentration at each of the filters being exposed at the same time. Where several, or all, filters must be exposed simultaneously to the aerosol, it is recommended that the aerosol be introduced at the blower inlets or another location which will produce a uniform mixture over all of the filters. (POINT 1)
• Measure the upstream concentration immediately upstream of the filter being tested. Care must be exercised to assure that a uniform distribution of the challenge aerosol exists.
• When using a Laskin nozzle aerosol generator set the air supply pressure at a minimum of 138 kPa (20 psi). Determine the amount of airflow volume being challenged. Using Equation 1.1, calculate the quantity of Laskin nozzles required to achieve an upstream concentration level of 10 μg/L or greater.
• Place the generator distribution tube in the location as determined in POINT 1.

Equation 1.1 (SI): Required Number of Laskin Nozzles

N = C X Q / Z

Where:

N = Number of Laskin nozzles required

C = Required upstream challenge concentration (greater than 10 μg/L)

Q = Airflow volume being challenged (L/min)

Z = Constant = 3823 x 100 = 382,300 L/min

Equation 1.2 (IP): Required Number of Laskin Nozzles

N = C X Q / Z

Where:

N = Number of Laskin nozzles required

C = Required upstream challenge concentration (greater than 10 μg/L)

Q = Airflow volume being challenged (cfm)

Z = Constant = 135 x 100 = 13,500 cfm

The constant Z is based on one Laskin nozzle producing 100 μg/L of challenge aerosol in 3820 L/min (135 cfm) of airflow.

• Note: When using more than one Laskin nozzle, the resulting aerosol generation may not be linear.
• Caution should be exercised when determining the upstream challenge when using multiple Laskin nozzles. It may be necessary to verify the actual concentration in mg/L with multiple Laskin nozzles based on each aerosol generator.
• Measure the upstream aerosol challenge concentration, using either a linear or logarithmic photometer scale.
• Set the photometer to full scale (100%) and measure the upstream concentration. The concentration should be established using one or more Laskin nozzles adjusted to produce an upstream concentration of 10 to 20 micrograms per liter of aerosol.
• Once the correct aerosol concentration is established, adjust the photometers gain such that the concentration established represents 100% upstream concentration.
• Increase the sensitivity of the photometer to a scale where 0.010% of the upstream concentration can be easily read.
• The filter face and the perimeter of the filter assembly shall be scanned by passing the probe in slightly overlapping strokes so that the entire area of the filter is sampled. The probe shall be held approximately 25 mm (1 inch) from the area to be tested during scanning. Separate passes shall be made around the entire periphery of the filter, along the bond between the filter pack and the frame, and around the seal between the filter and the device, at a scan rate of not more than 0.05 m/s or 5.0 cm/s (10 fpm or 2 inches per second). This assumes an airflow filter face velocity of 0.46 to 0.56 m/s (90 to 110 fpm). If airflow filter face velocities are significantly different, the scan rate shall be calculated using the information found in the current edition of IEST-RP-CC034, HEPA and ULPA Filter Leak Tests.

ACCEPTANCE:- An unacceptable leak is defined as a sustained reading greater than 0.010% of the measured upstream challenge concentration.

FIND MORE AT…

https://www.topas-gmbh.de/wordpress/dateien/page/Cleanroom_eng.pdf

http://www.ispe-pcc.org/uk/7-may-2008-hepa-filtration-specification.pdf

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