DR. JOHN C.ZAK,
PROFESSOR AND CHAIR DEPARTMENT OF BIOLOGICAL SCIENCES, TEXAS TECH UNIVERSITY.
THE TEST USED E coli INTRODUCED TO EXHAUST AIR FROM A AMERICAN AIR SCRUBBER IN A TEST CHAMBER DESIGNED FOR TEXAS TECH UNIVERSITY. 60 MINUTES WAS TIME OF TEST WITH RESULTS BEING LOGGED EVERY 10 MINUTES. AT NO TIME WAS PARTICULATES INTRODUCED DIRECTLY TO UVC LAMPS OR UVC-ASSISTED REACTORS.
TEXAS TECH UNIVERSITY
Department of Biological Sciences
Lubbock, TX 79409
April 14, 2005
This letter is to provide an assessment of the results we have obtained to date on the air purification unit you provided. Our goal was to evaluate the efficacy of the unit to kill selected bacteria. In the results that are provided in this letter, all experiments used E. coli as the test bacterium.
Experiment 1; Two plates of T-soy agar with a 10-6 dilution of E. coli added per plate were placed within two inches of the TiO2 filters. The open side of each Petri-Dish faced the TiO2 filters and did not receive UV light. Two plates were exposed per exposure times.
Treatment Exposure Time Colony Count per
Control 1 0 TNTC TNTC, Control 0 TNTC,
Plate 1 A 20 min 325 255 -Plate 1B 20 min 186 - Plate 2A 40 min 154 132 - Plate 2B 40 min 110 - Plate 3A 60 min 27 15.5 - Plate 3B 60 min 4
Treatment average plate
TNTC = to numerous to count
Experiment 2: Three plates were established in the same manner as described in experiment 1.
However, exposure times from 10 to 60 minutes were evaluated at 10 minute intervals.
Treatment Exposure Time
Control 1 0 TNTC TNTC - Control 0 TNTC
Plate 1 A 10 765 715 - Plate 1B 10 621 - Plate 1C 10 760 - Plate 2A 20 560 552 - Plate 2B 20 429 - Plate 2C 20 668 - Plate 3A 30 358 345 - Plate 3B 30 328 - Plate 3C 30 351 - Plate 4A 40 280 257 - Plate 4B 40 162 - Plate 4C 40 329 - Plate 5A 50 152 145 - Plate 5B 50 62 - Plate 5C 50 221 - Plate 6A 60 72 52 - Plate 6B 60 16 - Plate 6C 60 70 - (Min)
Colony Count per plate
These two experiments demonstrate that the exposure of the TiO2 filter to UV was able to kill growing E. coli cells with maximum kill after 60 minute exposure. The E. coli cultures were not exposed to the UV light.
Please do not hesitate to contact me should you have any questions concerning these results.
Dr. John C. Zak
Professor and Chair