To submit requests for assistance, or provide feedback regarding accessibility, please contact

Science & Tech

The ISS: Life Support Systems

Chris Hadfield

Lesson time 12:39 min

Learn about the many systems that work together to keeps astronauts alive aboard the ISS and how those systems are evolving so that we can travel even further in space.

Chris Hadfield
Teaches Space Exploration
The former commander of the International Space Station teaches you the science of space exploration and what the future holds.


Inside the space station right now, there are six people, living and working, running the experiments, exercising to keep their bodies strong. Breathing in, breathing out. Every time you breathe in, almost a magical thing happens in your lungs, where your body extracts the oxygen from the air and then extracts the carbon dioxide from your blood and does an exchange, so that when you breathe out, it's a different gas. You breathed in oxygen-rich, you breathe out some certain percentage of carbon dioxide. And here on earth, that's not such a big deal, because the entire planet is evolved to expect that. We have plants that take the carbon dioxide and process them using the energy from the sun and photosynthesis to release oxygen. It's a lovely big balance that's evolved on the planet. But what do we do on a spaceship? When you breathe out in space, how does that wasted or poisonous gas of carbon dioxide get reabsorbed? And where does the new oxygen come from? It's one of the problems we needed to solve. The best answer would be if we could just have a mini earth, and somehow completely recycle our oxygen. Maybe we could fill the whole space station with trees, and that way we could just use photosynthesis and the natural processes. But even if you-- say you planted beans. If you have a crop failure, everybody dies. And so, at least in this stage of space exploration, rather than counting on being able to grow plants to do that chemical transformation for us, we thought it would be better if we built machinery that we can count on and repair. And so on board the space station, we have carbon dioxide removal equipment. There are various ways to trap the gas, and through absorbent beds and different type of chemical processes to extract the carbon dioxide from the air. And if we do it properly, then we can separate the carbon from the oxygen, release the oxygen back into our atmosphere again, and then either trap the carbon or get rid of the carbon. And there are designs that trap that CO2 and then rotate the trapped gas to the vacuum of space, heat it so that it releases the gases you don't want and still keeps the oxygen, and then release the gas of oxygen back into the ship. But it's still not perfect. No machine is perfect. No recycling program is 100% perfect. And so in addition to doing the best we can to maintain the oxygen on board, we also have to bring up oxygen from Earth. Every resupply ship that comes up-- every one of these little ships that comes up and docks-- brings some quantity of fresh oxygen from Earth. Sometimes just the air that's inside it. Sometimes we've over pressurized that thing so that it's bringing just a free little bit of oxygen. Or sometimes, we actually bring up oxygen in pressurized tanks, even liquid oxygen, at times, in order to be able to resupply the ship to keep us healthy on board. To go to Mars, we aren't going to be able to resupply our oxygen on board. We're going to have to continue to invent ...

About the Instructor

Impossible things happen. At age nine, Chris Hadfield knew he wanted to go to space. He eventually went there three times, becoming a commander of the International Space Station. In his MasterClass, Chris teaches you what it takes to explore space and what the future holds for humans in the final frontier. Learn about the science of space travel, life as an astronaut, and how flying in space will forever change the way you think about living on Earth.


Students give MasterClass an average rating of 4.7 out of 5 stars.

This was some of the most inspirational and spiritual guiding experiences I’ve ever encountered over a simple array of videos. I knew I was getting into something awesome with Chris Hadfield but I didn’t expect that. It was marvelous.

Great masterclass, very inspiring, excellent perspective.

Preparation is key, in these types of situations, where you're at the edge of your abilities, at the edge of the technology or knowledge, it is the practice, the work and the focus that get you the end result, not your smarts or your luck.

What an amazing class!! Going to space has always been a dream of mine. Thank you Chris Hadfield for making your experience so real for me.


Bernardo F.

I agree, the ISS is and will be one of humanity's most important legacies. It's given us so much information about being in outer space, how to survive for long periods of time, as well as being a place where research can be conducted. I didn't know everything about the life support systems, and although I was sure most of the waste should be recycled, many things mentioned were new for me.


Most of the problems he mentions which are associated with sending crews to mars (entertainment / boredom, oxygen / fuel, capacity, payload, etc) center around that fact that it takes too long to get to Mars. Invent, and find a semi-safe way to launch this system in to space (get a better propulsion system on board), and we can focus instead on solving a whole new set of problems.

Mário Filipe P.

Lesson full of curiosities and fun facts, with great insight on ISS Life Support Systems. It's incredible the amount of challenges we'll need to overcome in order to move further away from our planet into deep Space!

Stephan G.

I believe the most important aspect of this fabulous series is its inspirational character and driving effect it can have on us. It reminds me of my college years when the engineering department invited well knows scientists for "inspirational" lectures every so often. Generally there was not much time to discuss nuts and bolts or go into great depth and details. On the contrary, it actually inspired you to go seek and find all these details yourself and search further, which by the way can be way more pleasant than getting everything dished up at once.

William D.

Atmospheric control is much more complicated than what has been described. What's the pressure of the ISS atmosphere? What is the % of Oxygen in that atmosphere? Pure oxygen or mixed gas? What is provided for sensing the purity of the atmosphere on board? What about other impurities from things like aerosol cans and carbonated beverages? Purifying the atmosphere is complicated. How about some more details? What is the efficiency of the ISS oxygen system. What are the details of the CO2 removal equipment. Are any other gases removed as well or are they controlled with regard to allow them on the ISS? Lastly, no mention is made of the consumable supplies and spares needed for this regeneration equipment. Yes we can purify the atmosphere but if you run out of the supplies to do that you're just as bad off as not having enough oxygen or water.


I love Chris's lessons and his enthusiasm for his work. He is a generous teacher and I am really enjoying his classes. But in the end, the moon and Mars are just rocks and dust. No doubt, there are commercial concerns interested in mining possibilities, but as far as alternatives to living on Earth there can be no realistic comparison. So far, Chris hasn't made his thoughts in this regard known.

Maddie W.

Really cool to learn about all the ways we are testing these technologies for future use. It seems like it might be a good idea to use machines as the primary life support system but perhaps plants/other biological systems could supplement that to increase the recycling efficiency. Or perhaps some day we could have enough plants on board that the machines would only sometimes need to be activated or used as a last resort. I agree with some of the earlier comments that these technologies would be very useful in places on Earth where resources are also less abundant. It's really amazing to think about all the ways astronauts in space are improving life for us back on Earth

Steve H.

I understand the need to recycle human waste products. It is a gently subject but I would be interested in the collection of both liquid and solid waste products in zero gravity.

James C.

"You know every sip of coffee - It's someone's urine you're looking at." True. No matter what drop of water you're dealing with, I think everyone *kindof* knows that (if they think about it for long enough)...but it must be a little odd to know the loop is so small that your cosmonaut buddy in the nearby module had a part to play in your next-morning java hit :-) Humans....

Alexis P.

Are we using the wasted gas as a propellant, because I didn't hear Chris mention anything? I mean you do have that in abundance up there, and the same goes for all space flights.