THB HOLLAND TUNNEL GRAY AND HAQEN 



603 



the inside fans have only 700 or 800 feet. These fans, during an 

 hour of heavy traffic, -will handle 84,000 tons of air, or 1,400 tons per 

 minute. They provide for changing the air in the tunnel 42 times 

 per hour. 



The fans are of the backward curved-blade type. Under diflFer- 

 ent conditions, one, two, or three fans may be operated on one tunnel 

 duct at anv one time. 



$'.g ^.■- ^opP'r capping. 



-fc- 



Lj 11 D 



FiouRK 4. — Typical vertical section through Tentilatlng building 



They are electrically driven by wound-rotor motors with resist- 

 ance in the circuit to make it possible to run them at variable speeds. 

 The combined capacities of the motors is approximately G,000 horse- 

 power, two-thirds of which will be in operation at times of maximum 

 load and one-third in reserve. Chain drives are to be used to make 

 possible speed adjustments or changes in the motors as well as on 

 account of the space limitations in the ventilating buildings. 



