Our project single floor mixed use space, with a large single heat recovery unit providing outside air to all of the spaces. Additionally there are 17 plenum return heat pumps located throughout the spaces used to condition the air in the spaces. Since all of the spaces are normally occupied, would we be required to take a (1) IAQ sample or (18) samples (17 heat pumps & 1 HRU). Sampling method wont work for our type of building, but I'm curious if the OA serving the space is considered the ventilation system or if the heat recovery unit and heat pumps are all considered seperate ventilation systems.