RE: [CAD_CAM_EDM_DRO] Shock Warning

Electronic Communication - Robert L. Shrader
Pg. 759-760

35-11 Electrical Dangers

Electric shock can range from 1mA for the threshold of feeling, to 5mA
for decided pain, to 10mA for the beginning of arm paralysis, to 30mA
for stoppage of breathing and possible death, to 75mA for ventricular
fibrillation (discoordinated heart beats) and probable death. With 4A
the heart may stop but may start again when current ceases. Above 5A
causes tissue burning, but may not be fatal if vital organs are not
involved.
A 5 to 10mA shock can cause a violent reaction that may throw a person
backward and possibly against some hard object or off a ladder, which
may cause injury.
Some appropriate skin contact resistances are: finger touch, dry, 50kR,
wet, 5kR; grasping wire, dry, 15kR, wet 5kR; holding pliers, dry, 5kR,
wet, 2kR; foot to wet ground through wet shoe, 5kR; hand in water, 300R.
Thus, standing on damp ground with wet shoes, holding a pair of pliers,
and touching a hot wire, the resistance to ground is perhaps 10kR. From
Ohm's law, E=IR, the voltage to produce a sharp pain would be .005 x
(10,000) or 50v. If the hand is perspiring, the voltage would be only
35v. Across 120v ac enough current might flow to produce respiratory
paralysis because after a short time the resistance of the body
decreases, increasing the shock current.
The path of the current determines how lethal a shock may be. Across a
hand or up one arm may not be lethal, whereas across the body and heart,
or involving the brain or backbone areas, shocks may be very dangerous.
One should always make sure not to be grounded when working with any
electrical equipment. (See also Sec. 17-32)
If someone is subjected to electric shock, the electricity should be
turned off before touching the person. If this is not possible, the
person should be dragged off using dry clothing or pushed away from the
circuit with sticks of dry wood or other insulating materials. Be very
careful not to get in the electric current too! If breathing has stopped
mouth-to-mouth resuscitation must be given immediately. If there is no
carotid (throat) pulse, CPR (cardiopulmonary resuscitation) must be
started at once. Everyone should be familiar with CPR and be able to
give it. Contact the Red Cross for CPR instructions and training.

Regards,
JJ

Be Kind, Be Careful, Be Yourself