Effectiveness and Reliability of UVC Sterilization~For~Surface Pathogens:~Fluorescent~Tubes vs~LEDs

The SARS-CoV-2 pandemic creates a need for safe, reliable, fast surfaced disinfection. UVC dissociates nucleic acid bonds in DNA and RNA of pathogens thereby killing them. Disinfection by UVC is fast and effective between 254-265 nm, and safer than 180-220 nm UVC which produces toxic ozone. UVC sources include fluorescent lamps and LEDs. Cost- and energy-effective UVC Fluorescent Lamps FL use toxic Hg vapor while solid state LEDs are compact and non-toxic. This work compares the power density PD stability and effectiveness of 254 nm UVC FL and 260-280 nm LEDs. A photodetector with a sampling area of 1 cm 2 probes PD, while 72 hrs incubation and Colony Forming Units (CFU) counting measures pathogen Kill Rate (KR). The PD of 3 identical FL and LED sources is measured 3 X for 60 s. every 10 s., a total 54 samplings. The PD measured mid- point on 10 cm long, 1 cm wide FL tubes varies by 30{\%} and increases by about 25{\%} over 60 s. PD measured on 3 sets of four 0.16 mm 2 LED vary by 12.5{\%} and show less than 1{\%} variation in 60 s. The KR of FUL and LED is 99.9 99{\%}. LEDs exhibit more reliable PD and KR.