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HOW MANY VOLTS TO KILL YOU?
Page 80
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Electrical dangers of workshop safety are sometimes overlooked—here an American correspondent writes of his experience in the USA
HOW much electricity is needed to electrocute a person, and how long must the current be applied? This is a problem of utmost importance for every part of the vehicle industry because electric current today is to this industry what water is to the human body. And most industrial electrical hazards are in the lower voltage range, 120 to 440V.
Accidents due to electricity are more dangerous on hot days when people are perspiring, or at other times in hot humid surroundings. The wet human body is a much better conductor than dry skin, Low voltages can be dangerous. They interfere with the mechanism of the heart muscle. They produce what we call "ventricular fibrillation", a disturbance of the muscular activity of the heart ventricles.
Low voltage current is hazardous particularly when the body contacting it is in a condition good for the passage of the current, for example when the skin is wet from heavy perspiration or drenching rain. Under thoroughly wet conditions the resistance of the skin may fall to as low as one-hundredth of its dry value.
On a warm summer day, to take one instance, the manager of a service station, who had suffered shocks before without harm, was working on a defective motor testing machine and touched a wire. He suffered an electric shock, this time feeling ill immediately. He vomited and went to hospital, where he complained of severe headache and suffered from a compulsive seizure. He had fever, his temperature was 102deg F, he could hardly breathe and he died 12 hours after admission.
In the case of high voltages (often used in industry for transmission and distribution) most contacts result in serious injury. As distinct from low voltages, they cause darnage through nervous centres—the heart stops beating, the lungs stop breathing. In the range from 1,000 to 7,500V, almost every contact which causes current to flow across the body will cause a non-breathing shock condition. However, half of these victims can be revived if artificial respiration is promptly started. Circuits of more than 7.500V, it is true, are a hazard even without contact, 'because the electric current is able to jump a gap in this range. Most highvoltage connections in industrial plants are found in the vaults containing the power feeds.
Recently some high-voltage accidents have been described where people came in contact with conductors carrying 45,000 to 50,000V. Artificial respiration had to be carried out for a long time. Some of these men actually recovered.
Workers both in the manufacturing industry and in vehicle workshops can be exposed to many low-voltage hazards as in some workshops there are: defective portable lights; defective electric cords which render the metal parts of machines alive; open switchboards and fuse boxes which were used in older installations; improper fusing; defectively built electrical equipment; many portable electric tools and machines.
The important precautions against electric shock are: never touch a swinging wire, it may be crossed with a "live" wire somewhere along the line, and shut a loosely dangling wire in a safe place with a rope until ready to connect it. Electrical equipment that has the insulation broken or that is "shorted" should immediately be repaired or replaced.
According to a report in the Journal of the American Medical Association, the intensity of the electric current was less than 110 m amp in two recent cases of fatal shock. Currents as low as 25 m amp have been fatal. But in other cases currents of many amperes have failed to cause death; they produced severe local burns in the extremities.
Why is there such inconsistency? It results from the different paths taken by the current within the body. Actually, the heart is the most vulnerable organ for the electric current. Interestingly enough, within each movement of the heart there is a period during which the heart is less susceptible to shock than it is at other times. For this reason, the exact instant of the shock is often all-important in deciding the outcome.
Damage from electric shock usually is either of a temporary nature, or it is fatal. Rarely will permanent damage remain after electric shock.
If you try to rescue a victim from contact with a live wire, turn off the electrical current first.
Use a long dry stick, a dry board, a dry rope or a rubber stick to remove the dangerous wire from the man. Stand on a dry board, or some other dry material Or use rubber boots. Don't use your bare hand without protection. Rubber gloves should be tested and rotated at least every month. Electrical workers for live work use "hot-line" tools which are mounted on long handles made of insulating material.
First Aid
For first aid after electric shock start artificial respiration immediately. Three or four hours of artificial respiration may be needed before success can be seen. Dr. Jellinek, a well-known authority on electrical accidents, mentioned a case when the interval between shock and returning consciousness was 90min.
Still more impressive is a Canadian report of a patient who recovered after continuous artificial respiration for eight hours after electric shock. As in all problems connected with electric shock, there is still a measure of mystery connected with the increased hazard of electric shock in some people.
"Save the Seconds and Save the Lives!" is an effective slogan used in the Life Saving Service. When artificial respiration has to he carried out for a long time, first-aiders should alternate.
If an electric shock is combined with burns, infection of the wound is prevented ,or kept to a minimum by clean first-aid methods. Don't touch the burn nor the gauze which will cover the burn.
Safety drives against electric current accidents are effective only if top officials participate in them. It has been shown that industrial companies where "really interested" top officials took an active part in the planned safety programme had 5.3 lost-time accidents per million man-hours; the term "top officials" includes officials of both management and union. However, on similar operation where no top officials had participated in the safety programme there were 128.7 lost-time accidents per million man-hours!