THE HOLLAND TUNNEL GRAY AND HAGEN 599 



chamber of 22G cubic feet capacity. Members of the staff spent 

 periods of one hour in air containing amounts of carbon monoxide 

 varying from 2 to 10 parts in 10,000. In addition, tests were per- 

 formed in a chamber of 12,000 cubic feet with an automobile en- 

 gine exhausting into the chamber. The duration of all tests was 

 one hour, whereas the length of time required to travel through the 

 tunnel at a speed of only 3 miles per hour is but 31 minutes. 



The results of the test showed that when an automobile engine 

 is running properly the exhaust contains no substance that is in- 

 jurious to any appreciable extent excejjt carbon monoxide. Gasoline 

 engines with cylinders missing, or when cold, over-supplied with oil 

 or gasosline, or smoking from any cause, may throw off disagreeable 

 vapoi"s irritating to the eyes and nauseating to some i)ersons. 



The physiological effects of carbon monoxide are wholly due to 

 the union of this gas with the hemoglobin of the blood. To the 

 extent that hemoglobin is combined with carbon monoxide, it is by 

 that amount incapable of transporting oxygen to the body. This 

 combination of carbon monoxide with the hemoglobin is reversible, 

 so that when a person returns to fresh air the carbon monoxide 

 is gradually eliminated. 



Of all physical signs and tests of carbon monoxide poisoning, 

 headache proved the most definite and reliable. Concentration of 

 gas too weak or periods of exposure too short to induce a headache 

 are to be considered harmless. No one had this symptom to an 

 appreciable degree after a period of one hour in the chamber with 

 four parts of carbon monoxide. With six parts the effect was usually 

 very slight, while with eight parts there was decided discomfort for 

 some hours. 



Hence a uniform concentration of four parts carbon monoxide 

 in 10,000 of air is designed to afford not only complete safety, but 

 also comfort and freedom from disagreeable effects. 



By the longitudinal method of ventilation, the entire tunnel would 

 be utilized as a duct for conveying air through the tunnel. Sufficient 

 air would be supplied through blower fans near one portal and would 

 enter the tunnel through a nozzle or nozzles at a velocity sufficient to 

 force it through its entire length. 



If in a 29-foot tunnel the air were introduced into the north tube 

 near one portal through a nozzle having a cross-sectional area of 74 

 square feet, and were exhaust<id through the opposite portal, the air 

 would h^ve a nozzle velocity of about 282 miles per hour. This 

 would produce a velocity of 72 miles per hour at points where the 

 roadway was occupied by a pleasure car and a truck abreast, or a 

 velocity of 51 miles per hour where there were no vehicles. Such air 

 velocities would be prohibitive in a vehicular tunnel, and the power 

 required to handle the air would be excessive. 



