2024 Volume 108 Issue 1 Pages 17-26
With the rapid spread of the novel coronavirus (COVID-19) infection, the early establishment of safe and low-cost virus inactivation technology has become an urgent issue. We have developed a mobile ultraviolet (UV) irradiation device that uses a low-pressure mercury discharge lamp made of quartz glass with a total length of 1,000 mm. This device emits light at an emission peak of 254 nm and is designed for efficient and cost-effective virus inactivation in unmanned environments, such as conference rooms and private rooms in commercial facilities. To assess the effectiveness of our device, we used the private rooms of commercial facilities of various sizes as model rooms (S-room; 2,001 mm (W)×2,166 mm (D)×2,500 mm (H), M-room; 1,989 mm (W)×4,042 mm (D)×2,500 mm (H), L-room; 3,172 mm (W)×7,889 mm (D)×2,700 mm (H)). We temporarily installed an UV irradiation device in each room and irradiated the rooms with UV radiation for 7 min in the S-room and 10 min in the M-room. Due to the size of the L-room, the UV irradiation was performed from two places. After UV irradiation at one place for 15 min, the device was moved and re-irradiated for 15 min. To evaluate the bactericidal effect of our developed UV irradiation device on various surfaces within the room, such as walls, floors, and ceilings, we measured the inactivation rate of E. coli and verified the device's performance. The results showed the inactivation rate of E. coli was 99.90% or more, except in areas where direct UV irradiation was obstructed by furniture. In addition, even in areas where direct light from the UV irradiation device did not reach, such as furniture, we observed a decrease in the survival rate of E. coli due to reflection from the walls. On the basis of the above verification results, we confirmed that the developed device efficiently inactivates bacteria and viruses within rooms used by an unspecified number of people, such as conference rooms and commercial facilities, in a short amount of time.
