A Simple Method for Evaluating the Performance of Louvered Fixtures Designed for Upper-Room Ultraviolet Germicidal Irradiation

ABSTRACT

The primary objective of the present work was to develop and validate a simple method for measuring the ultraviolet (UV) emission rate of louvered UV fixtures designed for upper-room ultraviolet germicidal irradiation (UVGI). A secondary objective was to compare the emission rates and energy usage of a few commercially available fixtures and explain the reasons for the differences observed. The ultraviolet emission rate of fixtures designed for upper-room UVGI is clearly an important metric for specifying the UV dosing requirements for a particular application—that is, determining how many UV fixtures should be installed in a given room. UV emission rate is also important for evaluating how efficiently the fixture utilizes the required electrical power input. The ratio of the UV emission rate to the electrical input is a useful parameter for ranking or improving fixtures. In this article, we describe “UV sensor traverse” and its validation. UV sensor traverse is a simple method for measuring UV emission rate by traversing the louvered face of a fixture with a UV sensor. Using this method, we show that a commercially available fixture with a cylindrical parabolic reflector with a tubular lamp has about 84% of the UV radiation exiting the fixture emitted from the back of the lamp, compared to only 21% for a fixture with a flat reflector and compact lamps. The energy-use efficiency of the former fixture is about five times greater than that of the latter fixture. In the fixture with the parabolic reflector, UV rays are redirected by the reflector so that they tend to be parallel to the louvers, allowing significantly more of the UV radiation emitted from the back of the lamp to exit the fixture than a fixture with a flat reflector, which simply alters the direction of the UV rays. To conserve energy and minimize the number of louvered UV fixtures required, well-designed parabolic reflectors are essential.

KEYWORDS:

• air disinfection
• upper-room GUV
• upper-room UVGI
• UV dosing
• UV emission rate
• UV sensor traverse

Notes

¹ Although Lumalier no longer manufactures the 72-W pendant fixture described here, this fixture had the same model number as the 72-W pendant fixture that Lumalier presently sells; however, the two fixtures have somewhat different exterior dimensions.

² If the detector does not have a flat rectangular surface, then a vertical index line can be placed anywhere on the cylindrical surface of the detector housing.

³ It is worth noting that for some UV meters, such as a model number IL1400A light meter with a model SEL240 detector (International Light Technologies, Peabody, MA, USA) that we initially attempted to use, the UV irradiance at the face of the louvers will exceed the maximum irradiance that the instrument is capable of measuring. In addition, if the optometer does not data log, it is recommended that one person move the UV detector while another person reads the optometer and records the measured irradiance in order to minimize errors.

Additional information

Funding

This work was supported by the Fogarty International Center of the National Institutes of Health (Award No. D43TW009379) and the National Institute for Occupational Safety and Health (Award No. 2R01OH009050).