I speak as a lay person who has been researching the same question so I have no special knowledge either of air con engineering or as a virologist.

However the main concern in what I have read is that the very conditions which make the air comfortable for humans do not actually help with the denaturing of the virus.

So the risk remains that if there is an asymptomatic carrier in the office shedding a high viral load and located by an air intake or outlet unit, then air containing this virus will be recirculated around the building and infect others who may be further than 2m away.

This is why the suggestion is for natural ventilation such as open windows has been made, as the air from outside is likely to be dry and subject to solar uv rays, both of which are factors thoiught to deactivate and denature the virus.

I look forward to hearing from subject experts who may be able to confirm or clarify.

Edited by user 21 May 2020 11:07:22(UTC)  | Reason: clarity of response

http://forum.iosh.co.uk/posts/t129786-Air-Con-Filters-and-Covid-19

http://forum.iosh.co.uk/posts/t129913-Ventilation-systems​​​​​​​