Safety in the workplace


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Those of us who got into the broadcast business years ago had very little training about safety procedures and guidelines. Early in my career, I watched a more experienced colleague get thrown across a transmitter building from attempting to measure plate current from an operating transmitter. Fortunately he was thrown away from the transmitter before any fatal injury ensued, but it made me acutely aware of two lessons: 1. Always have someone else in the room when working on a transmitter and 2. don't stick your hands in an operating transmitter.

A typical broadcast facility contains an unusually large amount of potential hazards — electrical, climbing, RF exposure, etc. And reductions in personnel mean engineers are working alone.

Large group owners now provide routine safety awareness programs, which can be valuable assuming the company backs up the training with the proper tools, support systems and resources.

If you haven't had awareness training, or have been doing this for awhile and have it figured out, it is worth mentioning just a few of the hazards that lurk in your facility.

Electrical safety

How many times does the transmitter decide to quit when you are awake and alert? My experience is that the call comes just after getting into a sound sleep. Let's not forget the majority of maintenance work also happens overnight.

We all know that shock occurs when one electrically places himself between a voltage source and a ground path. The rule of thumb has always been when working on electrical equipment, keep one hand in your pocket.

Figure 1 shows how humans experience the effects of electrical shock from as little as 1mA to 50mA when death can occur. Notice also that the trip current of the typical circuit breaker is about 15A. Ground fault breakers will trip under much lower current leakage conditions typically 5-500mA. You cannot depend on the circuit breaker to protect from lethal shock.

Table 1: Effects of Electrical Current in the Human Body

CurrentReaction
Below 1mAGenerally not perceptible.
1mAFaint tingle.
5mASlight shock felt; not painful or disturbing. Average individual can let go. Strong involuntary reactions can lead to other injuries.
6-25mA (women)
9-30mA (men)
Painful shock, loss of muscular control. The freezing current or “let-go” range. Individual cannot let go, but can be thrown away from the circuit if extensor muscles are stimulated.*
50-150mAExtreme pain, respiratory arrest, severe muscle contractions. Death is possible.
1-4.3ARhythmic pumping action of the heart ceases. Muscular contraction and nerve damage occur. Death likely.
10ACardiac arrest and severe burns. Death is probable.
15ALowest overcurrent at which a typical fuse or circuit breaker opens a circuit.
* If the extensor muscles are excited by the shock, the person may be thrown away from the power source.

-- continued on page 2



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