600 



ANNUAL, REPORT SMITHSONIAN INSTITUTION, 193 



In the distributive method of ventilation adopted for the Holland 

 Tunnel, the air is introduced into and exhausted from the tunnel 

 through a number of openings at frequent intervals leading from the 

 tunnel roadway. By this method fresh air is supplied at all points 

 throughout the tunnel. The air at any point can be controlled. 

 There is no discomfort or danger from high-velocity air currents. 

 The ventilation is not affected by traffic or the direction of the wind. 

 Exhaust gases are quickly diluted and removed. 



The space above and below the tunnel roadway is ideally suitable 

 for air ducts. Fresh air, supplied by blower fans at the shafts, is 

 discharged from the main duct under the roadway through adjustable 

 openings into continuous expansion chambers on each side, thence 



Figure 3. — Cross section 



lube or llolhind Tunnel 



through a continuous slot into the roadway. The air remains in the 

 tunnel an average of li/^ minutes as it slowly ascends . ' the ceiling. 



Exhaust fans located in the same buildings with the blower fans 

 draw the vitiated air through ports in the ceiling and thence through 

 the upper duct above the roadway, delivering it through stacks to 

 the outer atmosphere. 



Experiments to determine the coefficient of friction for flow of air 

 in concrete ducts, to verify formulae used in computing the power 

 required for moving air through a duct from which air is taken off 



