How do you continuously sanitize a coach/bus? Traveling on a coach during the COVID 19 pandemic was risky, and still is in some regions. There are many means of viral transfer; fomites via contact after touch of a surface, through direct droplet ballistics after a cough and finally through aerosolization of the sputum into the air. Clean hands and masks reduce the former two. Mitigating viral load aerosol accumulation within the coach is of personal, commercial and societal interest. Done correctly; the passengers are safer, the transport organization maintains hygienic business conditions and the society sees the viral spread reduction. UltraViolet Germicidal Irradiation (UVGI) has been in use in operating theaters and water plants for over 100 years to reduce viral and bacterial load in the air and water. Valeo’s Thermal Commercial Vehicles product group proposed, developed and now manufactures the most powerful coach/ bus UV Purifier module available. If the module is located within direct reach of the main air conditioning inlet, disinfected air is then delivered and entrained into the vehicle HVAC air delivery system. There it is cleanly distributed to the passengers and driver. During development there were two linked problems that surfaced; 1. Where do you put the module(s) in retrofit? 2. How do you keep the UVC levels sufficiently high enough to kill the SARS Cov-2 virus but then low enough for continuous driver and passenger daily exposure? The two problems can be modeled with CFD to gain insight in solving them. The latter limit problem is ok to formulate limits, but seems difficult to model initially. This paper deals with the slightly obtuse use of the third thermal heat transfer physics mechanism after conduction and convection. Reformulating the InfraRed radiation model into essentially monochromatic UV-C band radiation, and with thoughtful design allowed us to develop a very high intensity virus killer that was also perfectly safe in the vehicle cabin. The modules are sold world wide. Most importantly we use them daily on our team member transportation coaches to keep our employees safe to and from work at our production facilities.