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No. 8
Laskin Nozzle Aerosol Concentration
The purpose of this bulletin is to summarize
the basics of concentration expected from a Laskin Nozzle
aerosol generator, which includes the ATI Models TDA-4B, 4Blite
& 6C.
The standard Laskin Nozzle has four jets
located beneath four liquid feed holes. The amount of compressed
air required and amount of aerosol produced depends upon the
amount of compressed air applied to the nozzle.
The original research was conducted by Echols
and Young of the Naval Research Laboratory. This information
is covered in Naval Research Laboratory
Report #5929, dated 26 July 1963. From this and the Appendix
at the end of the Report, the concentration versus pressure
of the Laskin Nozzle can be extrapolated. ATI concluded that
with 20 psig nozzle pressure applied with 135 cfm of dilution
air, the output of one Laskin Nozzle provides a concentration
of 100 micrograms per liter. The data also indicates that
the nozzle requires 2.75 cfm of compressed air at this pressure.
Over the years, the impression has been that
the only way the Laskin Nozzle Generator can be used is by
applying 20 psig to the nozzle. According to the Echols &
Young Report, as you increase the pressure, the concentration
increases and as you decrease the pressure, the concentration
decreases. Further studies by Dr. Melvin First at the Harvard
School of Public Health and Wendell Anderson at the Naval
Research Laboratory have proved that by varying the pressure
up and down on the Laskin Nozzle, the aerosol size distribution
is not significantly affected. According to Wendell Anderson,
two of the jet holes may be plugged to obtain half of the
standard concentration. If three jets are plugged the concentration
drops to 1/4 of the standard output concentration. This information
is useful for customers who want to test air filtration systems
that are operated lower than 135 cfm and special applications
for certain types of filters which require low air flows.
Detailed information on the Laskin Nozzle
and its use is available in Section 8 of the U.S. Department
of Energy, Nuclear
Air Cleaning Handbook. Dr. First's reference is available
in the American Industrial Hygiene Association's 1983 Journal,
Pages 495 - 500. ATI presented a paper to the Institute of
Environmental Sciences (IEST) in 1993 which confirmed that
the liquid level did not have significant effect on aerosol
concentration. This data begins on Page 559 of the 1993 IEST
Proceedings, Volume I.
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