QUESTION TEXT: Until 1985 all commercial airlines completely replenished…
QUESTION TYPE: Most Strongly Supported
- Cabin air has been replaced once every hour since 1985.
- Before that it was once every half hour.
- Less frequent air changes lead to more carbon dioxide and easier spreading of airborne diseases.
ANALYSIS: We can say that that there will be some change in carbon dioxide levels and in disease levels. The effect will be stronger on longer flights.
We can be a bit more confident about the carbon dioxide levels. That’s because there are many factors in disease transmission rates (and they might have changed since 1985). There are not so many factors in how much carbon dioxide is in an airplane.
- Maybe? We don’t know why airlines replenished air less often.
- Maybe? Air replenishment is only one factor. We don’t know how important it is.
Secondly, people might be sicklier now. Lastly, we don’t know how long these flights are. If they are shorter than a half-hour then there isn’t much difference.
- We have no evidence for this. We don’t even know if it is the carbon dioxide that causes more illness or just the less frequent filtering.
- We’d like to think this is true, but maybe it wasn’t. Maybe even more frequent filtering is required.
- CORRECT. This is fairly strongly supported. Before 1985 the air would have been changed four times. Now it is changed twice.
Of course, there could be other factors that affect carbon dioxide levels. But this is just a most strongly supported question and not a must be true question.
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