These marines are being trained on how to react in different situations, such as losing vision with pepper spray and being tased. Just because you can’t see doesn’t mean you give up in battle. If you want to live you have to overcome the pain and make use of what you have. That attitude is exactly what the Marine Corp is trying to show these men and women.
Now, it’s always a bit comical to watch these things. If you were in the military, you probably have your own unique memories of the gas chamber and how you and those around you reacted. The yells, the snot, the works. However, one thing’s for certain… if you had a stuffy nose before entering the gas chamber, you definitely left with zero breathing problems. Great training, Marines! Keep it up!