A fall of ground caved the heading where a miner worked to within 30 ft (9.144 m) of the face. The heading is 5x 8 ft (1.524 x 2.438 m) in dimensions. How many hours could the miner can theoretically remain alive after the fall assuming a respiratory quotient of 0.9 Calculate based on the standpoints of oxygen depletion and suffocation from carbon dioxide. Which one governs?