Six safety tips for hotel quarantine

As anyone who has to fly during the pandemic knows, it is a stressful time.

There is the task of keeping safe on the aeroplane, numerous stages of COVID-19 testing and then of course, mandatory quarantine at the end of the flight. The endless supply of news articles on how, where and for how long hotel quarantine should occur just adds to these stress levels.

Because we can’t pause this travel during the pandemic – needing to move around the world to visit sick loved ones, for work, or of course to return home – we have devised a list of things travellers can do as individuals, to quarantine more safely.

We initially drafted this advice for friends and family going through hotel quarantine, and now share the information with anyone who may need it.

As mechanical engineers, our advice is focussed on airborne or aerosolised transmission of the COVID-19 virus – that is, the movement of micro-droplets released when you breathe or speak and that can remain in the air for what may be hours afterwards. This is different from the larger respiratory droplets that can be avoided by social distancing (the 1.5 metre rule).

Despite initial conflicting advice on whether-or-not airborne transmission is an issue, the science now supports that aerosols are a pathway for transmission, albeit at a lower risk than close contact.

Our first piece of advice (given the number zero because this should be done before your journey into hotel quarantine begins) is regarding masks.

Mask type and fit

0. Purchase N95 masks for your transfers and make sure they are fitted correctly. If procuring multiple N95 masks proves difficult, the Centre for Disease Control has some helpful advice for refreshing N95 masks; all you need is a breathable paper bag and at least 72 hours between uses.

Additionally practice the hand hygiene rules that you should have been using for the last year. All possible sources for catching the virus exist on the plane and your behaviour should reflect that.

However, there are two points that need to be considered, the first is that recent mutations of the virus appear to be far more infectious and can survive as an aerosol for 90 minutes.

The second is that statistics mean much less when you’re focusing on an individual or group of individuals – if you’re the unlucky 1 in 1000 to catch something, the statistics don’t matter for you anymore.

Breathing the same air as someone infected is your biggest worry in hotel quarantine, where direct infection paths have been almost entirely eliminated via physical isolation from others.

You can also see this with the positive case that appeared after the person left quarantine in NSW, or the numerous hallway security guards that may have acquired COVID from their time in the hallway.

In short, there is reason to believe that while you are in hotel quarantine, you still could catch COVID.

Reduce air movement from hallway into the room

We believe there is a slight misconceived notion from the public that air only moves out of a room when a door is open.

The reality is air is always leaving your room if there is a larger pressure in the room than in the hallway, moving along what is known as the ‘pressure gradient’ from high to low.

Of course, there is absolutely an increased amount of air leaving the room with an open doo, as seen in the smoke experiment pictured above.

However, it’s naïve to think this is only occurring when the door is open. Armed with this new knowledge, and a few other key findings from our ongoing research, we offer the following advice:

1. Turn the fan setting on your room’s ventilation system to maximum. Do whatever you can to get the most air flow into your room from a source other than the hallway, whether it be heat, aircon, or the ‘vent’ or ‘fan’ setting to circulate air from outside. Your comfort is second to creating the largest positive pressure in the room (you can always put on more jumpers and jackets if the airflow makes it too cold).

This should mitigate incoming air flow from the hallway as well as through the ceiling from adjacent rooms and will provide more clean air to your room.

2. Minimise time spent with open windows/sliding external doors. Outside the hotel will likely have a lower pressure than inside, so leaving windows/doors open will undo everything from Recommendation 1.

In some hotels your ventilation return can occur in your room through the mesh ceiling vent in the bathroom. Closing the bathroom door would limit some of this air return further increasing the positive pressure of your room.

Stay in your hotel room as much as possible

3. Hallways are where the air from all of the rooms ends up (due to higher pressure in the rooms relative to the hallways). The more time you spend breathing in the hallway, the more time you’re sharing air with other hotel quarantine guests.

4. Minimise door openings to the hallway and don’t open the door to anyone. They can leave whatever it is they want you to have at the door. You can speak through the door, including food delivery, cleaning supplies, security and open it after they have left.

Despite what we have previously highlighted about the large-scale pressure difference between the room and the hallway/outside, the act of opening the door (specifically the rapid motion of the door) creates a localised low-pressure region behind the door called a wake.

This wake can cause a small rush of air into the room as it follows the door, potentially containing both the smaller airborne particles that we have focused on in this article as well as the larger, more dangerous respiratory droplets, that stay very close to the person, to move into your hotel room.

In addition to opening the door after the person has left, one can further minimise this risk by opening the door slowly, creating a smaller wake, rather than quickly and forcefully which would create a larger one.

5. Minimise time spent in elevators and communal spaces like shared bathrooms with limited air flow. Have you ever noticed how stuffy most elevators are? That’s because there is almost no airflow in them. This means you’re breathing someone else’s potentially infected air that was exhaled in the minutes to hour before you entered range.

While taking these steps will help to reduce your risk from contracting an airborne case of COVID-19, it won’t eliminate it. It’s important to remain vigilant and not let your guard slip during quarantine.

And remember that while you are doing your part, scientists, doctors, and researchers worldwide are working to reduce airborne transmission of the COVID-19 virus and improve building ventilation to keep us all safer.

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