Ninety-nine percent of what you do in your job as a Fire Controlman , you will do around electricity. Since that makes you extremely susceptible to electric shock, it’s  very  important  for  you  to  know  the  basics  of electric shock, how to avoid being shocked, and how to treat victims of electric shock. The following section discusses those factors. This section discusses the severity, avoidance, and victims of electric shock. BASICS OF ELECTRIC SHOCK The following factors determine the severity of the effect electric shock has on your body: ·   The amount of body resistance you have to the current flow. ·   The path the current takes through your body. ·   The  length  of  time  the  current  flows  through your body. Body Resistance Resistance varies greatly in different parts of your body. A value of 1,500 ohms is commonly used as the resistance  between  major  extremities  of  an  average human body: hand to hand, or hand to foot. For example, suppose you accidentally grabbed a wire carrying 120 volts alternating current (V ac). We can use Ohm’s law, I = E/R, to figure how much current would flow through your body: E = 120 V ac (the voltage you grabbed) R = 1,500 ohms (your average body resistance) Therefore: I  =  120/1,500  amp I  =  .080  amp I  =  80  milliamperes Therefore,  if  you  grabbed  a  120-V-ac  wire,  80 milliamperes  of  current  would  flow  through  your body! Table 3-1 shows the effects of varying amounts of electric shock on a normal person. In our example, you grabbed  80  milliamperes  of  current! That  is  15 milliamperes beyond what could be fatal. It is also 70 milliamperes beyond the “can’t-let-go” threshold for a 120-pound person and 62 milliamperes beyond what is needed to cause you to stop breathing. Remember,  the  1,500  ohms  is  just  an  average value.  Body  resistance  varies  from  person  to  person and  may  often  be  less  than  1,500  ohms.  When  your skin is moist, your body resistance could be as low as 300  ohms!  Also,  breaks  in  your  skin  at  the  point  of contact  could  reduce  your  skin  resistance  to  nearly zero! Skin  resistance  is  only  important  when  you  are handling  voltages  of  less  than  240  volts.  If  you  get shocked by more than 240 volts, the voltage arc will burn  through  your  skin  and  leave  deep,  third-degree burns where it enters your body. Current Flow Path The two most dangerous paths that current can take through your body are (1) from hand to hand and (2) from  left  hand  to  either  foot.  The  second  path  is  the MOST dangerous since the current will flow through both your heart and other vital organs. Current Flow Duration Fibrillation  is  the  shocking  of  your  heart  into  a useless flutter. The longer you are shocked, the more chance there is for your heart to begin fibrillating. Most people   who   die   from   electric   shock   die   from fibrillation. Fibrillation in a normal adult is unlikely if the current in milliamperes is less than 116/t, where “t” is the shock duration in seconds. The longer you are shocked,  the  less  current  is  needed  to  cause  heart fibrillation. 3-2 CURRENT (milliamperes) HUMAN REACTION (at 60 Hertz) 1.1 PERCEPTION: A slight tingling sensation. CAN’T LET GO: Arm and hand muscles close involuntarily: 10.0 16.0 A 120-pound person. A 175-pound person. 18.0 CAN’T BREATHE: PARALYSIS OF THE CHEST MUSCLES. 65.0 HEART FIBRILLATION: Rapid, irregular contractions of the heart muscles. Could be fatal. Table 3-1.—Effects of Electric Shock