Page:New York subway ventilation.djvu/14

12 compartments in order to so act. Since this is not the case there results simply an agitation of the air with some slight and casual expulsion of air through these louvres and vent chambers.

Diagram D shows the so-called refrigerating plant at the Brooklyn Bridge. Cost of Fan Operation

In order to get some comprehension of the initial, and operating cost of such blowers, which, according to the Chief Engineer, were operated by motors ranging from 15 to 30 H.P., it will be seen that, assuming an average of 20 H.P. apiece, 500 H.P. per hour would have been required according to the Chief Engineer for removing the 60,000,000 cubic feet of air within the subway between the Battery and 96th St. and thereby change its cubic contents once every half hour. A very little arithmetic shows that this would amount to $120.00 for every 24 hours of continuous fan operation on the assumption of a cost $.01 per H.P. per hour. It cannot be questioned that 25 such blowers so driven

Diagram C

would exhaust from the subway the amount of air specified, but especial attention is called to the fact that this does not by any manner of means insure that the cubic contents of the subway "from the Battery to 96th St.," would ever be changed even once in a year—for the very obvious reason that an amount of air exactly equal to that exhausted by the fans must, and will, flow back into the subway through the openings nearest to the fans and would, unless provision be made therefor, result in short-circuiting of the air and thereby practically defeat the plan and only partially relieve the conditions at a few points.