185nm is a short wavelength, it produces ozone and it travels through the air in a very short distance; which means can not directly impact the pathogens.  222nm can destroy pathogens with limited travel through the air while producing the least damage in human skin and eyes. Its penetration capability is very short, that is why it causes the least damage to human eyes. 254 nm is the most effective in penetration as well as in kill rate without ozone production. (Ozone produces reactive oxygen species that travel in air for sanitization process, however, exposure is not recommended for humans and not permitted in UVC products in Canada) 280nm is the border of UVB range, with much reduced kill rate.