We Can Kill COVID! Here's the Proof., page-72

Also the neutraliser filter only popped up when the FRG units were fitted into in-room prototypes. PO3, before engaging with OEMs , were looking at air cleaning as a larger scale application of retrofitting to existing building HVAC systems, not desktop gadgets.

a 5 year old article but still with a read that identifies many of the problems of ozone / ioniser air cleaning gadgets, problems which have been mostly ignored rather than resolved by the products on the market today. The article states that with all these shortcomings HEPA is the way to go. So yes HEPA is the main rival for PO3 rather than the flawed ozone / ioniser products currently on the market. https://learn.allergyandair.com/ozone-generators/

PO3 are also developing the FRG unit with the intention that very little adaptation to the core unit is required to apply it across air, water and surface applications