The word duct doesn’t appear here because far-UV installation is most useful (compared with other wavebands) for whole-room application—agree that UV in ductwork has the potential to be very useful, but you’d use a longer wavelength if people weren’t going to be directly exposed, because you can crank up the power on longer UVC wavelengths without producing tons of ozone. (Far-UV is specifically 200-230 nm, but UVC goes up to 280 nm.) I focus on far-UV because the excitement about far-UV specifically has to do with whether there’s potential for it to be installed in such a way that it can stop in-room pathogen transmission before air entirely circulates or recirculates, which could be a big deal for pandemic prevention.
Why in-duct UVC isn’t more widely employed: I don’t know a ton about its current adoption level but retrofitting ductwork is a hassle, even just in the simple sense of needing to contract technicians to do it. Anyway, its efficacy isn’t guaranteed; you need to know the power of the light you’re getting, which many consumers are not equipped to assess. The efficacy is a combination of the light’s power and the speed of airflow through the duct, UV lights are often sold at an insufficient power to effectively disinfect air, and consumers can’t necessarily evaluate whether it was a good investment (common problem across air cleaners in general).
My guess is that we’re still on the leading edge of ordinary consumers thinking of air quality as something that they can and would want to control for anything beyond comfort, particularly for pathogen (or allergen, or mold) removal. All air quality tech faces that problem (and my blog post was trying to address the problems far-UV faces beyond that). Anecdote I found interesting: Some colleagues attended a global indoor air quality conference earlier this year and reported that something like 80% of the sessions were about comfort in the indoor environment, while about 5% were about pathogen control.
The word duct doesn’t appear here because far-UV installation is most useful (compared with other wavebands) for whole-room application—agree that UV in ductwork has the potential to be very useful, but you’d use a longer wavelength if people weren’t going to be directly exposed, because you can crank up the power on longer UVC wavelengths without producing tons of ozone. (Far-UV is specifically 200-230 nm, but UVC goes up to 280 nm.) I focus on far-UV because the excitement about far-UV specifically has to do with whether there’s potential for it to be installed in such a way that it can stop in-room pathogen transmission before air entirely circulates or recirculates, which could be a big deal for pandemic prevention.
Why in-duct UVC isn’t more widely employed: I don’t know a ton about its current adoption level but retrofitting ductwork is a hassle, even just in the simple sense of needing to contract technicians to do it. Anyway, its efficacy isn’t guaranteed; you need to know the power of the light you’re getting, which many consumers are not equipped to assess. The efficacy is a combination of the light’s power and the speed of airflow through the duct, UV lights are often sold at an insufficient power to effectively disinfect air, and consumers can’t necessarily evaluate whether it was a good investment (common problem across air cleaners in general).
My guess is that we’re still on the leading edge of ordinary consumers thinking of air quality as something that they can and would want to control for anything beyond comfort, particularly for pathogen (or allergen, or mold) removal. All air quality tech faces that problem (and my blog post was trying to address the problems far-UV faces beyond that). Anecdote I found interesting: Some colleagues attended a global indoor air quality conference earlier this year and reported that something like 80% of the sessions were about comfort in the indoor environment, while about 5% were about pathogen control.