Estimation of the error factors in irradiance measurements of electromagnetic sources inside disinfection cabinets

Abstract

Periodically testing the performance of any biological safety cabinet or other sterilization chambers is mandatory; hence, the importance of evaluating the effects of error factors on this performance arises. Until now, despite the necessity of disinfection against many microorganisms, particularly protection against the current pandemic, international standards for the manufacturing and evaluation of safety cabinets did not recommend testing the ultraviolet C performance inside these safety cabinets. The main aim of this paper is to use the sensitivity coefficient as one of the essential terms in uncertainty evaluation, to study the effect of different distances and tilt angles on the irradiance and, hence, the uniformity inside the cabinet or chamber. It was found that the homogeneity of the distribution of irradiance levels along the irradiated area was significantly affected by the distance and angle. The results obtained utilizing the sensitivity coefficient indicated that a simple increase in distance will result in a considerable loss in the irradiance value reaching around 30%. Every 5° increment in the tilt angle causes a decrement in the irradiance value by about 14% compared to the original value (0°); hence, the uniformity decreased significantly by around 45%. These effects may reflect on the sterilization performance of the cabinet as an essential process. At the end of this paper, due to the importance of considering these measurements and the effect of the two parameters on irradiance and, hence, the uniformity, the author recommends that these measurements be added to international standards for safety cabinets manufacturing and evaluation. The recommendation may help to focus more on evaluating the ultraviolet C homogeneity performance inside biosafety cabinets.