Without being an engineer or architect, I've stayed in a lot of hotels over the year, and often been able to look in their nooks and crannies. Basically the rooms themselves are often small structures within the larger structural elements of the hotel. The air spaces are common over many rooms/spaces, and you wouldn't consider rooms to be isolated from one another in any meaningful way. I'd see them as being almost the worst possible places for this sort of quarantine.
Being an engineer myself and also familiar with HVAC and the like I would offer the following
generalisations.
Early on it was considered that CV19 was not aerosolising unless there were invasive procedures like intubation, or patients with very high viral loads, or with concentrated number.
Given that, and with the need to find somewhere reasonably suitable and as hotel rooms were empty and available using them
as an initial solution was quite a reasonable initial expedient solution. Having people quarantine at home, while quite possibly individually reducing risk also had the huge risk that people would not actually quarantine properly and would go out as did occur.
However later it was realised that aerosolisation was sometimes occurring. And I would also note the comments from people such a Bloomfield and Sutton that people are not equally contagious and that most transmission will come from a relatively small number of positive cases.
Now with commercial building, buildings like offices will have false ceilings and that any party walls popped up will in the main just be dividers. This false ceilings will often be porous, and can be popped up to access cabling, ducting and the like. Ata wall junction lift up the ceiing panel and you will be able to reach over to the other side quite freely. When leases are signed normally the whole floor will be open and the tenant put in their own party walls , and at make good will revert back to the full open plan. Air and sound will often be a lot freer to move around.
With hotels and apartments (unless a conversion from a previous use) the walling will normally be completely different. While these walls will not be normally be structural (at least in tall buildings) the walls and ceilings will in most well built buildings be separate cells with reasonable barriers to air movement, sound etc.
In assessing a hotel suitability for HQ it would be a simple matter to check if rooms are indeed individual cells, or just really an open floor with wall dividers. Those that were not in essence separate cells should not have bee used.
The HVAC if well designed will be pushing air in and drawing out of each room, and not through a chain of rooms. However doors are not airtight, and on opening you can see shifts in air due to pressure differences that can result for a number of reasons. So in the nebuliser case the aerosolised infected air could float out into the corridor if the door is opened, or slowly through the gaps in around the door.
With a commercial type ceiling, that should not be in a well built hotel, aerosolised air could float up through the ceiling and travel around partitions. Moreso when the HVAC is not running, and it should be noted that HVAC in may building will not be operating 24/7.
Open widows and doors can also be a huge problem wit air pressure flows, and to my thinking the HQ used in Qld that had the inter-room transmission was not at all suitable due to this reason. All those large sliding balcony doors left open could easily cause pressure differences that would push or pull air into the corridors and through other rooms. People standing on adjacent balconies often quite close both horizontally and vertically and the wind can push the virus further. So while "fresh-air" may have been considered to be good for individuals to be outside and to have fresh air coming in, it will also have meant that contaminated air would also be freely travelling in and out of rooms not through the controlled HVAC ducting, but through the corridors.
With what we know now, and with time on our side as I posted not long ago we really should have moved to separate cabin quarantine. Especially, ones where you just have them self-catered and fully stocked with food on arrival so that there is minimal mixing of the quarantined with quarantine staff outside rooms (really it should just be on arrival, departure and health checks, and no other mixing including people being in corridors). That hotel rooms are still being used over a year since the pandemic started as quarantine facilities is extremely poor.
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