Learning Objectives

• Identify the appropriate safety practices to be used around microwave transmission facilities

• Explain safe practices for the use of high-band radio antennas

• Recognize that power-line carrier work requires the same safety practices as work on energized lines

Lesson Description

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Exposure to radio frequency hazards can be harmful to humans, and there are over 500,000 radio frequency emitting devices, like cellular phone towers, across the U.S. now.

INTERNATIONAL BROTHERHOOD OF ELECTRICAL WORKERS

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Electrical workers cannot see, hear, or smell the danger from radio frequency (RF) radiation, or electromagnetic radiation, which is why this hazard is cause for concern and heightened awareness. There are basic warning signs to observe and safety precautions to be taken into consideration when contact with structures emitting these forms of radiation is expected.

Typical microwave and power line carrier communication equipment can be very powerful and cost-effective but, as with working with many other energy sources, certain safety procedures must be followed to keep the electrical worker free of related dangers. The Occupational Safety & Health Administration (OSHA) specifically addresses microwave signaling systems. Here are some basic safety guidelines to follow when working near such equipment.

Basic Safety Guidelines When Working Near Microwave Signaling Systems

First, for the safety of electrical workers, radio frequency equipment owner and operators must remember that if the electromagnetic radiation level within an accessible area is greater than 10 milliwatts per square centimeter, as averaged over any possible 0.1 hour period, then such an area must have a clearly visible, posted warning sign. This standard pertains to equipment presenting the risk of both whole body and partial body irradiation.

Electromagnetic Radiation Warning Sign

• The sign must contain the symbol for radio frequency (RF) radiation hazards, consisting of a red triangle above an inverted black triangle, separated and outlined by an aluminum color border.

• The words “Warning—Radio Frequency (RF) Radiation Hazard” must appear in the upper triangle. The lower half of the warning sign must be labeled: “Radiation in this area may exceed hazard limitations and special precautions are required. Obtain specific instruction before entering.”

If employees must work in an area where the radiation could be excessive, the employer must take measures to ensure the safety of employees. These could be job procedures (administrative controls) or physical barriers to keep the exposure below the maximum level (engineered controls). But workers need to remember they are at greatest risk from exposure, and work accordingly; deciding against entering a posted or a suspicious unmarked area unless they personally know that it is safe, is an example of working with sensitivity to the radio frequency (RF) radiation hazard. Workers must use personal protective equipment(PPE), follow the procedures, and be sure to know what they are doing, with an acute sense of where they are in relation to any RF hazard.

Because of the need to protect vision, workers are prohibited from looking into an open waveguide or antenna that is connected to an energized microwave source.

Another major consideration, some communications systems use the power line itself to carry signals between equipment at different points on the line. OSHA therefore requires that all work associated with power line carrier installations, including work on equipment used for coupling carrier current to power line conductors, must be performed according to the requirements for work on energized lines.

Key Terms

• Energized
  Electrically connected to a source of potential difference, or electrically charged to as to have a potential significantly different from that of earth in the vicinity.

• Equipment 
  A general term including material, fittings, devices, appliances, fixtures, apparatus, and the like used as a part of, or in connection with, an electrical installation.

• Personal Protective Equipment
  A system used to prevent an employee from falling. It consists of anchorages, connectors, body belt/harness. It may include, lanyards, lifelines, and rope grabs designed for that purpose.

• Workplace 
  Any plant, yard, premises, room, or other place where an employee or employees are employed for the performance of labor or service over which the employer has the right of access or control, all work places covered by industrial insurance.

• Qualified Person
  Qualified Person, Attendant or Operator. A person designated by the employer who by reason of training, experience or instruction has demonstrated the ability to safely perform all assigned duties and, when required, is properly licensed in accordance with federal state, or local laws and regulations.

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