Fresh Air Intake

I've a question on the Fresh Air calculation, with the following scenario... a) An office has total of 100 employees, including 5 managers; b) We allocated 95 work stations (open office, 95 chairs) for the non-managers, and 5 managers' rooms; c) Each manager room has 1 chair for the manager, and 3 chairs for a round tables (total 4 chairs, for small discussion); d) There is also a small break area, which can has 10 chairs; e) There is another meeting room with 15 chairs. Summary: The total employees is 100, but the total chairs is 95 + (5 x 4) + 10 + 15 = 140 chairs. Note: The AC we use is FCU and dedicated ducted fresh air without any CO2 control . Question: Do I calculate fresh air based on the total 100 persons OR by each of the rooms and open office, which is coming to 140 chairs?