Question 648 Deck Safety

The correct answer is C) 21%. The normal percentage of oxygen in air is 21%. This is the standard composition of air, with nitrogen making up the majority at around 78% and other gases like argon and carbon dioxide making up the remaining 1%. This 21% oxygen composition is the baseline that is used for regulatory purposes, including in the US Coast Guard Captain's License Examinations. The other answer choices are incorrect because 16% is too low for normal air, 18% is also too low, and 25% is too high for the typical oxygen content in the atmosphere.