Air purifiers work best in a closed room environment, but this makes some people worry that closing windows starves us of oxygen. Yet recent tests in a real apartment — with as many as seven people in a small room — show less than 1% change in oxygen levels in a closed room.
Fears of Closing Windows and Low Oxygen
Fears of low oxygen levels are easy to find. For example, question-answer site Quora asks whether running an air conditioner in a closed room leads to low levels of oxygen.
Playing on this belief, companies rushed in with products that fill this supposed void. For example, a popular air purifier in China called “Three Dad’s” claims to solve the oxygen problem by using “submarine technology” to create oxygen.
The logic of this fear is simple: The room is closed, humans breathe in oxygen, so oxygen levels should decrease over time, right?
Closing Windows: The Oxygen Experiment
Smart Air tested this question by tracking oxygen levels with an iBrid MX6. We used the Smart Air office as an extreme testing site because the humble Smart Air office has seven people packed into just 34.5m² room.
On top of that, the office windows and doors are sealed with insulation tape to prevent polluted air from getting in (the office has no central air system). We tracked oxygen levels throughout normal workdays, keeping the door shut except for when people left and came back from lunch at midday.
Closing Windows Has Virtually No Effect on Oxygen
Even in these extreme conditions, oxygen levels showed almost no change. By the end of the day, oxygen levels had dropped by 0.3%.
Most homes have far fewer people in them, and the doors and windows aren’t sealed up with insulation tape like ours are. So changes would be even smaller in most homes.
Simply put, humans don’t take in as much oxygen as we think we do. Based on oxygen alone, estimates are that the average person could survive in a completely sealed room for 12 full days!
The Change Is in Carbon Dioxide
While oxygen levels are pretty much constant over the day, what does change is the amount of carbon dioxide in the air. We tracked CO2 levels using the Air Visual Node, which showed carbon dioxide more than tripling throughout the day.
How Can Carbon Dioxide Triple When Oxygen Remains Unchanged?
If humans breathe in oxygen and breathe out carbon dioxide, how can one remain almost unchanged while the other skyrockets? The key is that regular air has a lot more oxygen than carbon dioxide.
Oxygen is about 20% of air, while carbon dioxide is only 0.038% of air. Thus, carbon dioxide is capable of tripling from such a small number, while oxygen is mostly unchanged.
Carbon Dioxide Can be Harmful
Although we don’t have to worry about running out of oxygen, too much carbon dioxide can be harmful. The levels in the Smart Air office during the test (1,000-3,500PPM) can make people feel drowsy. These levels may even worsen people’s performance on cognitive tests.
Three Simple Ways to Lower CO2 Levels
#1 Open your windows from time to time
Opening the windows will let CO2 out, but it will also let air pollution in. However, it may be easy to fix. Our tests have found that strong purifiers like the Cannon and Blasts for example can cut PM2.5 by 50% in just 10 minutes after closing the windows.
#2 Leave the windows open a tiny bit
If you have a strong purifier, open the windows by just a bit and leave it there. Our tests have found that purifiers can still be effective even when the window is left open. This is even easier with a super-powerful purifier like our Blast air purifiers.
#3 Get a place with a central air system
Choose an office or apartment with a central air system that brings in outdoor air (and hopefully filters it!). If your apartment or office–like many offices in China–doesn’t have a central air system, you can get an air exchange system installed, but it is expensive.
Thomas is an Associate Professor of Behavior Science at the University of Chicago Booth School of Business and the founder of Smart Air, a social enterprise to help people across the world breathe clean air without shelling out thousands of dollars for expensive purifiers.