Watch these Marines take part in a training exercise in a gas chamber. The process looks pretty painful as they can be seen in the room for several minutes continually taking off and putting back on their mask during the exercise.
This is a common exercise for United States Marines since it teaches them how to survive in an environment that contains a deadly or hazardous substance. The exercise usually lasts between 3 and 5 minutes depending on how well the Marines deal with the situation.
Do you think you could last as long as these marines did? Let us know in the comments below!