Thread by @AlanBixter

So: What is Wrong with COVID-19 Hotel Quarantine in Australia? A thread.

After difficulties with compliance to COVID-19 stay-at-home orders for returning travellers, Hotel Quarantine became the mainstay of infection management for these people in Australia. /2

But the efficacy of this program has varied enormously between states. Here I argue that the key difference lies in ventilation. /3

Think, for a moment, about the hotel rooms you have stayed in: Most would be serviced by one of two types of air handling: a) Natural ventilation modified by a split system air conditioner; or b) A mechanical (ducted) ventilation system. /4

Natural ventilation requirements are dealt with in Section 3 of AS 1668.2, which refers to BS5925. There are three methods that can be used to calculate requirements, but for the sake of brevity, I will refer only to one: Prescriptive opening size and location. /5

I will take the most problematic design that has full compliance with the Standard: In an enclosure containing 2 people with low metabolic activity, & over 2 square metres of floor space/occupant, openable openings must be no less in effective area that 10% of floor area. /6

The critical issue is that in cold weather, the occupants may choose to leave these openings closed. /7

Mechanical (ducted) ventilation systems are dealt with in Section 4 of AS 1668.2. There are two methods that can be used to calculate requirements; I will only discuss the most problematic example of the most simple method. /8

The prescriptive procedure incorporates minimum mandatory requirements for single enclosures (e.g. a hotel room): In an enclosure containing 2 people with low metabolic activity, & a room temperature at or below 27C, the outdoor air supplied should be >5 L/s/person. /9

In some cases, exhausted room air is partially reused to supply air for low occupancy spaces, such as corridors. /10

Clearly, as a generalisation, these standards are adequate for hotel rooms. However AS 1668.2 has many mechanisms for accommodating air-borne contaminants, which might not be considered in the case of low occupancy hotel rooms. /11

I would argue that as the point of Quarantine is to contain infection, with the clear expectation that some travellers will be infected. /12

The transmission of SARS-CoV-2 occurs via four routes: Direct contact, fomites (inanimate objects), droplet and aerosol. Analysis of super spreader events shows that most can probably be attributed to aerosol concentration in poorly ventilated spaces. /13

The standards for mechanical ventilation of enclosures for health care functions is given in Section 6 of AS 1668.2, & those for Infectious Isolation Rooms in paragraph 6: /14

The minimum outdoor airflow rate delivered to Infectious isolation rooms should be the greater of 10 L/s/person and 2 L/ square metre & should have a controlled room air pressure that is lower than that of adjacent enclosures. /15

Given that these requirements are much more demanding than those for low occupancy residential purposes, the majority of hotels are unlikely to meet them or be suitable for quarantine. /16

Distributed accommodation of separate cabins or bungalows, temporarily modified to ensure high natural ventilation, may be an effective alternative. /17

And one hotel style common in Queensland may also be relatively effective, as it consists of external corridors and naturally ventilated rooms, often ventilated by sliding doors to a balcony, which in warm weather, are often opened. /18

And this last point may be the most significant reason for the large difference in efficacy between hotel quarantine programs between the colder southern, and warmer northern states in Australia – incidental differences in ventilation adequacy between hotel designs. <end>