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Hotel air is recycled breath
Carrying monitors everywhere
For three years, a small group of people has carried CO2 monitors through flights, hotels, and restaurants. Outdoor air sits around 422 parts per million of carbon dioxide. A flight measured 1,900 the whole way, and a subway car can reach 5,000, where one in every 10 breaths is someone else's exhalation. Schools have terrible air quality because their HVAC systems aren't working well.
What high levels do
Anything north of 1,500 parts per million has been shown to have serious cognitive effects: lower test scores, anxiety, and higher blood pressure for some people. A Harvard study found 50% lower test scores above that level. A reading of 500 is great, and anything up to 1,000 is very good.
Why hotels recycle air
Hotels glue their windows shut because recycling air that has already been heated or cooled is far cheaper than conditioning air from outside. Some LEED-certified green buildings and wellness hotels, which recycle air to conserve energy, recorded atrocious air quality, and friends who went back to the same hotels recorded the same numbers.
Why does CO2 build up in sealed rooms?
Exhaled breath is roughly 4 percent carbon dioxide, about 40,000 parts per million, far above the outdoor level near 420. In a closed room that gas has nowhere to go, so the reading climbs with every person and every hour. Ventilation standards, such as those from the engineering society ASHRAE, set a minimum amount of outdoor air per occupant to hold it down. CO2 is used as a stand-in for how stale a room's air is because it is easy to measure.
What did Harvard find about CO2 and thinking?
In a 2016 study from the Harvard T.H. Chan School of Public Health, office workers spent days in controlled rooms with different CO2 levels. At about 950 parts per million, their scores on decision-making tests were around 15 percent lower than in the cleanest conditions. At about 1,400 parts per million, scores were around 50 percent lower in some areas. Strategy and crisis-response tasks showed the sharpest drops.
Why is the air on a plane so stale?
Aircraft cabins mix fresh air drawn in through the engines with recirculated air. The recirculated portion passes through HEPA filters, which trap particles but cannot remove carbon dioxide. A full cabin puts the breath of hundreds of passengers into a small volume. Manufacturers state that cabin air is replaced within a few minutes.
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