This bulletin provides a summary of the basics of concentration expected from a Laskin III-A Nozzle aerosol generator, which includes the ATI Models TDA-4B, 4Blite, 6C & ATI 6D.
The standard Laskin III-A Nozzle has four jets located beneath four entraining holes. The volume of compressed air required to produce a given amount of aerosol is dependent upon the pressure of compressed air applied to the nozzle.
The original design research was conducted by Echols and Young for the Naval Research Laboratory. This information is covered in NRL-5929 (1963) Studies of Air-Operated Portable Generators. Using this report and its Appendix, the concentration versus pressure of the Laskin Nozzle can be extrapolated.
Using the report information, it can be shown that when 20 psig is applied to the nozzle and diluted with 135 cfm of air, the output of one Laskin Nozzle provides a concentration of 100 micrograms per liter of DOP. The data also indicates that each nozzle requires 2.67 cfm of compressed air to maintain the 20 psig pressure drop.
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 shown that by varying the Laskin nozzle pressure up and down, the aerosol size distribution is not significantly affected. Wendell Anderson also concluded that two of the jet holes may be plugged to obtain half of the standard concentration. Also, if three jets are plugged the concentration drops to one-fourth of the standard output concentration. This information is useful for testing air filtration systems that operate at lower than 135 cfm and other special low-flow applications.
More 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 to 500.
Also, ATI presented a paper to the Institute of Environmental Sciences (IEST) in 1993 confirming that the liquid level did not have significant effect on aerosol concentration. This data begins on Page 559 of the 1993 IEST Proceedings, Volume 1.