Airplanes do an excellent job circulating air, and are relatively safe places to be. Your risk in the terminal and the taxi greatly exceeds your risk on the plane.
I used to agree with this. But I recently realized it likely isn’t true. Consider the following:
Based on this paper, I’d say that an air change rate 0.5 ACH is a fairly low estimate for an airport terminal.
So if the airport terminal is about 30 times less crowded than an airplane (as measured by number of people per unit volume of air), then all else being equal, the risk of covid for each hour spent in the terminal would be comparable to that in the airplane. It’s more complicated because the air in the airplane is mixed better than in the terminal most likely. But I think the airplane is actually way more crowded than the terminal, by a factor orders of magnitude larger than 30. Airport terminals typically have high ceilings. Overall, I think the terminal is much safer per unit time than the airplane, even considering the better ventilation on the airplane.
On top of that, the air filtration on an airplane is often turned off while the airplane is sitting at the gate.
How much does the air near the ceiling of the terminal actually help? If the virus particles instantly circulated evenly, then they would definitely help. On the other hand, if there isn’t much air current (as is the usual case in airport terminals) then the air near the ceiling is useless, since any virus particles would stay in the air near people’s mouths and noses.
The math might still work out in favor of the terminals, but I’m not convinced.
I agree that the degree of air circulation within the terminal is an important factor. I’m not certain that the terminal is safer than the plane, but I think more likely than not the terminal is safer.
This link from my previous comment is not exactly a peer reviewed article, but it suggests that the difference in air replacement rate in a well-ventilated versus poorly-ventilated space (the terms they use for mixture of the air, not for air change rate) is only about a factor of 3. Of course, there are different degrees of poor ventilation.
I would be really interested to hear the perspective of somebody with greater expertise in the relevant engineering and physics.
I used to agree with this. But I recently realized it likely isn’t true. Consider the following:
The time to remove an airborne contaminant depends on the Air Change Rate (measured in Air Changes per Hour, or ACH) and how well the air is mixed in the space.
Air in an airplane cabin has an air change rate of about 13 to 15 ACH. (Actually, the one paper linked in this bullet makes my overall argument pretty well, though it doesn’t reference airport terminals)
Based on this paper, I’d say that an air change rate 0.5 ACH is a fairly low estimate for an airport terminal.
So if the airport terminal is about 30 times less crowded than an airplane (as measured by number of people per unit volume of air), then all else being equal, the risk of covid for each hour spent in the terminal would be comparable to that in the airplane. It’s more complicated because the air in the airplane is mixed better than in the terminal most likely. But I think the airplane is actually way more crowded than the terminal, by a factor orders of magnitude larger than 30. Airport terminals typically have high ceilings. Overall, I think the terminal is much safer per unit time than the airplane, even considering the better ventilation on the airplane.
On top of that, the air filtration on an airplane is often turned off while the airplane is sitting at the gate.
How much does the air near the ceiling of the terminal actually help? If the virus particles instantly circulated evenly, then they would definitely help. On the other hand, if there isn’t much air current (as is the usual case in airport terminals) then the air near the ceiling is useless, since any virus particles would stay in the air near people’s mouths and noses.
The math might still work out in favor of the terminals, but I’m not convinced.
I agree that the degree of air circulation within the terminal is an important factor. I’m not certain that the terminal is safer than the plane, but I think more likely than not the terminal is safer.
This link from my previous comment is not exactly a peer reviewed article, but it suggests that the difference in air replacement rate in a well-ventilated versus poorly-ventilated space (the terms they use for mixture of the air, not for air change rate) is only about a factor of 3. Of course, there are different degrees of poor ventilation.
I would be really interested to hear the perspective of somebody with greater expertise in the relevant engineering and physics.