The gas mask design and its components may lead to these respiratory load issues. At rest and effort, what would be the impacts for the work of breathing and gas exchange? In order to avoid hypoxemia and hyperoxia, what would be the optimal means to restore proper oxygenation? We hypothesised: i. on a heightened WOB and the respiratory demands related to wear of the gas mask; ii. An occurrence of hypoxemia will be manifesting during a continuous period at both at rest and effort.