Inhaling two atoms of hydrogen and one atom of oxygen, as produced by a hydrogen fuel cell, is considered safe and unlikely to cause health problems due to the minimal quantity involved. However, inhaling a mixture of hydrogen and oxygen from tanks can be dangerous, potentially leading to severe injuries if ignited. The mixture can be safe for breathing under controlled conditions, such as in deep scuba diving, where it helps mitigate nitrogen narcosis. Despite its safety in small amounts, hydrogen is not commonly used in diving due to the risks associated with ignition. Overall, while small quantities from fuel cells are harmless, caution is advised with larger concentrations.