RF Safety Signs
RF safety signs should be used wherever there is the potential for human exposure to exceed applicable exposure limits and to minimize risks to human safety. RF Safety Solutions' signs provide guidance concerning potential RF safety hazards, tower registration information, and to control the use of cellular phones.
RF safety signs and their correct usage can be confusing. RF Safety Solutions is here to help you select the appropriate signs for your application. You may also find it useful to read Richard Strickland’s magazine articles on the subject. See Magazine Articles and Radio World Spotlight Articles.
RF safety signs are made from aluminum panels with rounded corners and a mounting hole in each corner. The signs have a special UV-resistant coating applied to their surface to increase their life in outdoor environments. Most of the signs are 12” x 18” (30.5 cm x 45.7 cm). The most popular signs are also available in Spanish and in a smaller size suitable for mounting on interior doors. The small signs are 8” x 12” (20.3 cm x 30.5 cm). The bilingual signs for Canada’s Safety Code 6 are 24” x 18” (61.0 cm x 45.7 cm).
RF Field Level Signs
RF field level signs come with three different action words at the top of the sign: NOTICE, CAUTION, or WARNING. The signs related to RF fields are based on the Maximum Permissible Exposure (MPE) limits established by the Federal Communications Commission (FCC). The FCC has two tiers of MPE limits for RF field levels. The more restrictive limits are for General Population/Uncontrolled exposure. The NOTICE sign refers to fields that may exceed this level. The CAUTION and WARNING signs refer to fields that may exceed human limits—the FCC MPE limits for Occupational/Controlled exposure. The Tower CAUTION and Water Tank CAUTION signs refer to RF field levels on the tower or water tank. The three basic signs refer to field levels “beyond this point.”
Use this sign to mark locations where RF field levels may exceed the FCC MPE limits for General Population/Uncontrolled exposure but are definitely below the FCC MPE limits for Occupational/Controlled exposure. Available in 12" x 18" and 8" x 12" sizes.
Use this sign to mark locations where RF field levels in some areas of the site may exceed the FCC MPE limits for Occupational/Controlled exposure. Available in 12" x 18" and 8" x 12" sizes.
The strong language used on this sign is designed to mark areas with very high RF field levels. This sign is rarely needed to mark ground-level sites. No access should be allowed into areas marked by this sign unless power has been reduced or the transmitter has been shut off. Available in 12" x 18" and 8" x 12" sizes.
Use this sign at the base of a tower. This sign is ideal for applications where the RF field levels on the ground beneath the tower are insignificant, and the risk potential is only for personnel who climb the tower. We recommend this sign for virtually all tower sites with the exception of AM radio towers. Available in the 12” x 18” size only.
Use this sign at the base of a water tank. This sign is ideal for applications where the RF field levels on the ground beneath the water tank are insignificant, and the risk potential is only for personnel who climb the water tank. Available in the 12” x 18” size only.
Use this sign to mark locations where RF field levels may exceed the FCC MPE limits for General Population/Uncontrolled exposure but are definitely below the FCC MPE limits for Occupational/Controlled exposure. Available in the 12” x 18” size only.
Use this sign to mark locations where RF field levels in some areas of the site may exceed the FCC MPE limits for Occupational/Controlled exposure. Available in the 12” x 18” size only.
The strong language used on this sign is designed to mark areas with very high RF field levels. This sign is rarely needed to mark ground-level sites. No access should be allowed into areas marked by this sign unless power has been reduced or the transmitter has been shut off. Available in the 12” x 18” size only.
Burns and Contact Currents Signs
RF burns can result from excessive RF contact currents. Two signs are designed for the most common applications. RF burns are a very serious concern when working near an AM radio tower. Very high RF voltages and currents are present on the tower, at the feed wire from the tuning hut, and inside the tuning hut near the tuning circuits. These high levels are also present inside the phasor cabinet. Contact currents, and potentially modest shocks, can occur when a person touches a tower guy wire. Guy wires are normally insulated close to the attachment point on the tower. However, unless an additional insulator is used a few feet above the ground (just out of reach of an adult), significant RF contact currents can flow from the guy wire through the person making contact. This is because the guy wire can act as a receiving antenna and pick up substantial energy from the transmitting antennas.
Use this sign at AM tower sites—one on the gate to each tower enclosure. Use a sign near a feed wire if it is within reach of a person standing on the ground. Available in the 12” x 18” size only.
Use this sign near guy wires that do not have an insulator a few feet above the ground at sites with high-power antenna systems. Available in the 12” x 18” size only.
Tower Registration Sign Kit
Since 1996, the Federal Communications Commission has required that towers be registered. The FCC also requires the tower registration number to be posted on each tower. The typical solution for tower owners has involved the design and production of custom signs. The Tower Registration Sign Kit is comprised of an 8” x 12” (20.3 cm x 30.5 cm) aluminum sign and a set of vinyl numerals. The exterior-rated numerals are self-adhesive. The sign is shown in the sidebar on the right.
Canadian Safety Code 6 Signs
RF safety signs should be used wherever there is the potential for human exposure to exceed applicable limits. These signs are designed to meet the requirements of Health Canada's Safety Code 6, which sets exposure limits for two classes—RF Workers and Other than RF Worker. These large, 18” x 24” (40.5 cm x 61.0 cm), signs provide guidance information in both English and French. Three different action words are used at the tops of the signs in accordance with the requirements of Safety Code 6. These action words, in order of risk potential, are: NOTICE, WARNING, and DANGER.
Cellular Phone Use Signs
The use of cellular phones can be disruptive to others. In areas where sensitive electronic medical equipment is used, cellular phone usage can actually cause these medical devices to malfunction. Medical device interference is a bit complicated, but it can be a source of significant problems in hospitals and for people who have pacemakers, defibrillators, and other types of implanted medical devices. See Medical Device Interference for more information.
The NOTICE CELLULAR PHONE Sign is designed to be used in hospitals and other facilities where the use of wireless devices is restricted. Available in 12" x 18" and 8" x 12" sizes.
The INFORMATION CELLULAR PHONE Sign is designed to be used anywhere that the use of wireless devices can be considered disruptive, such as movie theaters, hospitals, churches, schools, and restaurants. Available in 12" x 18" and 8" x 12" sizes.
The TURN OFF CELLULAR PHONE Sign is designed to be used to curtail disruptions from cell phones. Available in the 8" x 12" size only.
RF Safety Solutions Can Help
Call us to discuss your sign application or contact us to request a quote.