Two Deaths Stress Manhole Danger
A manhole incident that took the lives of a fire fighter and a civilian in Montgomery County, Md., emphasizes the dangers associated with unventilated enclosures and the precautions that must be observed.
Because a hydrant being used by construction company workers was leaking and water was flowing into an apartment building, a call was made to the Hillandale Fire Department last October 30. Captain S. T. Mullican and Sergeant David W. Shaw went to the scene in a fire department station wagon to investigate. A light rain was falling at the time, and the temperature was 59 degrees.
At about 1:30 p.m., soon after arrival at the scene, Shaw checked an open manhole some 250 feet from the hydrant and saw a man slumped in a water meter pit. Shaw called to Mullican and then went into the pit to help the victim.
Mullican radioed for assistance and then went to the manhole, where he saw Shaw also slumped over in the pit. Mullican tried to enter the manhole, but he was physically unable to do so while wearing a self-contained breathing apparatus. Other fire department personnel arrived and, after donning masks, were able to get into the 10-foot-deep pit and remove the two victims.
Both Shaw and the construction firm worker, Chester Miller, were pronounced dead on arrival at Washington Sanitarium Hospital.
When Fire Marshal Robert Smith and Fire Prevention Officer M. Thomas Slater of the Montgomery County, Md., Division of Fire Prevention arrived at the scene about 3:30 p.m., Slater checked the pit with negative results. The manhole cover had been put back in place after the removal of the two victims and was removed to make the gas check.
Carbon dioxide present
When the pit was checked by technicians of the Washington Suburban Sanitary Commission, it was found to contain only about 10 percent oxygen. Washington Gas Light Company technicians also checked the pit and recorded about 18 percent oxygen and 13 percent carbon dioxide. They reported no indication of carbon monoxide, methane, or any other combustible gas.
Don Courtney of the Washington Gas Light Company said that his firm checked the pit again on November 2 and recorded concentrations of 12 to 14 percent oxygen and 6 percent carbon dioxide. Washington Gas Light’s safety director, Ira Farmer, said that the tests made on November 2 confirmed the low concentration of oxygen detected on the day of the fatal incident. He said the last time the manhole cover was known to have been removed was about a month before, when the meter was read.
Dr. John S. Rogers, acting medical examiner for Montgomery County, reported after autopsies were performed that both victims died of asphyxiation due to the low concentration of oxygen and the high concentration of carbon dioxide. He also stated that the toxicologist in the State Medical Examiner’s Office in Baltimore said that the concentrations of carbon dioxide found in the pit would cause paralysis of the respiratory center in the brain with but two or three breaths even with a normal amount of oxygen present.