User manual FIELD CONTROLS 4291UV-AIR

[. . . ] This device is designed to irradiate the air as it circulates through the home, so the single pass evaluation is the worst-case scenario use of this device. The air in the home will pass through the heating and air conditioning system many times a day, as the air is circulated throughout the home. Knowing the effectiveness of the UV-Aire in a single pass application, enables us to project how effectively the device will treat the air with multiple passes a day. [. . . ] The airflow velocities were measured at the center of the duct at the intake end of the test duct. Page 3 ORGANISM APPLICATOR: An atomizing humidifier spray nozzle mounted at the center of the test duct intake was used to distribute the organism into the air stream. UV DEVICE: A Field Controls UV-Aire air purifier model UV-18 was mounted onto the center of the side of the test duct 6 feet from the exit end of the chamber. The lamp is a UVC germicidal lamp (non ozone producing) 18 inches long with a UV output rating of 73 µW/cm2 at 1 meter from the lamp. AIR SAMPLING METHOD: An Andersen N6 single stage "bioaerosal" sampler was used to take the air samples and distribute the sampled air onto agar medium. The Anderson sampler method requires corrections to the actual colony counts on the plates. This provides a more accurate measure of the bacteria per cubic foot of the sample air. In the following tables, the Serratia marcescens Positive Hole Count values are the actual plate counts and the Corrected Particle Count values are corrected value based on Anderson correction tables. Test Apparatus Figure 1 Page 4 Testing Procedure The testing was performed in two stages. (See table 1) This developed the control data or the base line bacterial levels for the comparison. (See table 2) Two airflow rates were used to evaluate the lamp effectiveness based on exposure time. Airflow velocities through the ducts of a typical residential heating and cooling system range from 300 to 500 feet per min (fpm). To decrease the exposure time, a second test was conducted with the airflow in the duct doubled to 1000 fpm. Since the effectiveness of UV lamps is based on the UV light output and exposure time, doubling the airflow reduces the effectiveness of the lamp. The bacterium was cultured and the cells harvested to provide a suspension of known cell density. This was further diluted to provide gallon quantities of a test suspension containing an estimated 95, 000 CFU/ml. This suspension was pumped through the spray nozzle mounted in the center of the duct inlet. Five air samples were taken for each of the test velocities at short intervals (typically ½ to 2 minutes). This produced a large sample volume of air and reduced the levels of back ground bacteria and molds counts. The plate counts (colony forming units or CFU) for each of the five tests were totaled and divided by the total test volume of air. [. . . ] At the higher velocity, the lamp still reduced the bacterial levels by at least 71 % at a 50% decrease in the exposure time. Since the reduction efficiency is based on lamp UV output and exposure time, the assumption can be made that decreasing the exposure time to the UV light is similar to testing an organism that requires a higher UV energy requirement to kill the bacteria. The log reductions in bacterial levels were very close to theoretical values. [. . . ]