How many plants would you need to generate oxygen for yourself in an airlock?

You probably wouldn't survive long in an airlock. But what if you had some plants in there? Could they keep you breathing comfortably?

We've learned that there are two problems with being in an airlock. The first, running out of oxygen, is relatively minor. In a ten by ten foot room, you should be fine for three days. The major problem is breathing out carbon dioxide, which at concentrations of about two percent - at standard atmospheric temperature and pressure - will kill you.

The easiest way to keep yourself alive in an airlock would be to stock it with plants. But how many plants are enough? This is a harder problem to solve, because there are endless variables. One of the most vexing ones is the fact that plants produce less oxygen as carbon dioxide levels increase. They produce different amounts of oxygen at different phases of their growing cycle. They take in different amounts of carbon dioxide at different temperatures. And finally, some plants only "breathe," at night in order to save water - which if you are in a perpetually lit room or are killed after only half a day doesn't do you any good at all.

Scientists estimate a safe oxygen consumption of 50 liters per hour for a human. Meanwhile, a leaf gives off about five milliliters of oxygen per hour. A person would need to be in a room with about ten thousand leaves. About 300 to 500 plants would produce the right amount of oxygen, but it's much harder to estimate the amount of carbon dioxide the plants absorb, especially if every time a person breathes out, they inhibit oxygen production. To be safe, don't get into an airlock without bringing about seven hundred potted plants with you.

Image: PD Photo, Jon Sullivan

Via Department of Energy and Astronomy Cafe.