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Dosimetry of Room‐Air Germicidal (254 nm) Radiation Using Spherical Actinometry
Author(s) -
Rahn Ronald O.,
Xu Peng,
Miller Shelly L.
Publication year - 1999
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1999.tb08142.x
Subject(s) - actinometer , optics , radiant energy , opacity , radiation , integrating sphere , irradiation , fluence , standard illuminant , dosimetry , materials science , chemistry , physics , nuclear medicine , nuclear physics , laser , medicine , plasma
A method is demonstrated for measuring germicidal (254 nm) ultraviolet radiation (GUVR) in an omnidirectional manner. This method has application for those situations in which GUVR from more than one direction or source impinges on a three‐dimensional object, and when it is of interest to determine the radiant fluence experienced by the object. For this purpose spherical quartz vessels were constructed varying from 0.8 to 1.25 cm in outside diameter. The vessels were filled with an actinometric solution consisting of KI and KIO 3 . This solution is optically opaque at 254 nm and is insensitive to room light. Upon exposure to GUVR this solution, which counts all of the 254 nm photons, forms triiodide. Following radiation, the contents of the vessel are removed, the absor‐bance of triiodide measured and the fluence rate determined based on a relationship that takes the volume to cross‐sectional area of the actinometer into account It is demonstrated that, in accordance with theory, the area of the sphere that intercepts the radiant energy is equal to the cross‐sectional area of the sphere. A demonstration of the utility of this method was carried out in a test facility 90 m 3 equipped with five GUVR lamps, one in each corner and one in the center of the room, arranged so as to irradiate the air in the upper portion of the room. Twenty spherical actinometers were evenly distributed around the room and exposed for either 30 or 90 min. The fluence rate varied from one part of the room to another, peaking near the GUVR lamps at 65–85 uW per cm 2 . By averaging over all 20 points, a pseudoaverage fluence rate for the room was found to be 42 and 44 u.W per cm 2 for the 30 and 90 min exposures, respectively. The similarities in the values for this metric demonstrates that the actinometric response is linear over this exposure range.