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Archive for March 1st, 2018

Originally published in the Pacific Coast Bulletin, February 28, 1924

Ventilation problems make up a big share of all questions asked in state examinations for firebosses and mine foremen. Following are two typical questions with the correct answers.

QUESTION—What is the rubbing surface of an airway 8 x 12 ft., in section, its length being 6,550 ft.? (b) If the velocity of the air is 350 ft. per min. what is the volume of air in circulation?

ANSWER— (a) The perimeter of the airway being 2 (8 + 12) = 40 ft. and its length 6,550 ft., the rubbing surface is 6,550 x 40 = 262,000 cu ft. per min.

(b) The velocity of the air current is then 262,000 ÷ 330 = say 794 ft. per min. (more…)

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