Wouldn't the system somehow need to detect the virus at incredibly low PPM, and rely on the virus being in that section of the room? Especially with coronavirus, which travels via water droplets and falls to the ground fairly quickly, you could have a spreader walk through the room without it hitting the device.
I'd also expect that the list of viruses that are worth evacuation over is much much shorter than the sum of all viruses in the air at one time. (Looked it up, looks like 219 viruses that can even just infect us[1] vs hundreds of millions [2])
It'd be absolutely terrifying - a totally invisible threat setting off an alarm that's telling you there's a danger in your immediate vicinity. And then what? The office building fire drill, where hundreds of people all trudge down 20 stories together in the claustrophobic confines of a concrete stairwell along with the unconsciously contagious? Or lock down the room until someone can decontaminate the whole thing?
I'd also expect that the list of viruses that are worth evacuation over is much much shorter than the sum of all viruses in the air at one time. (Looked it up, looks like 219 viruses that can even just infect us[1] vs hundreds of millions [2])
[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3427559/
[2] https://www.virology.ws/2013/09/06/how-many-viruses-on-earth...