Monitoring RF safety - TvTechnology

Monitoring RF safety

Limiting human exposure to non-ionizing radiation (NIR) is an important concern for the communications industry.
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Limiting human exposure to non-ionizing radiation (NIR) is an important concern for the communications industry. Both the FCC and OSHA have rules and regulations regarding human exposure to NIR with which the communications industry must comply. In pursuing compliance, broadcasters can enlist the aid of numerous articles that have been written about NIR, many of which offer mathematical formulas to determine RF power densities and estimate their effects on humans. In addition, advances in technology have eased the broadcaster’s job of protecting employees and contractors. But despite this help, many broadcasters find that the FCC and OSHA rules and regulations are difficult to apply on a day-to-day basis, which has caused some confusion in the industry about how to comply. To address these issues, this article offers a plain-English discussion on several compliance topics.

First, broadcasters must realize that compliance with FCC rules and regulations regarding human exposure to NIR must be extended to include compliance with the OSHA safe working standards. In other words, after achieving compliance with FCC rules, some additional steps are required to comply with OSHA rules.

The FCC’s plain-English explanation of its rules and regulations regarding NIR is provided in Bulletin 65, Human Exposure to Non-ionizing Radiation (OET65), from the FCC’s Office of Engineering and Technology, available at www.fcc.gov/oet/rfsafety/. The document fully explains the mathematics necessary to determine compliance, and understanding it should not be difficult for any RF engineer. But implementing safe working procedures based on those calculations can be difficult. OET65 does a good job of initiating discussion on a broad range of the topics, but it fails to present clear solutions to many of the issues it raises.

As a condition of licensing, nearly all licensed broadcasters should have been compliant with the new OET65 rules by Sept. 1, 2000. These rules are “new” primarily in that they are an extension of the rules that have governed broadcasters for several years – they have been expanded to include licensees above 100MHz. Not much has changed with respect to the basics of RF exposure, except that the rules have become somewhat more stringent. One fact has remained constant: Broadcasters must take action to ensure that people are not exposed to radio frequency radiation (RFR) in excess of the FCC limits. OSHA (on both state and federal levels) has become more actively involved in the industry. Officially, OSHA has exposure limits on record that are different from the FCC’s, but it publicly supports the new FCC limits and recognizes them as reasonable and appropriate.

Generally, OSHA compliance requires broadcasters to create a written health-and-safety policy to identify potentially unsafe work areas that may expose workers to NIR levels above the 100 percent maximum permissible exposure (MPE) level, and to develop safe working practices for anyone who needs access to those areas. OSHA considers the written health-and-safety policy the cornerstone of compliance. The overall purpose of the written document is to adopt clear, concise policies on how the site will be administered and what steps will be taken to ensure worker safety. It must include practical and real-world considerations, including the ability of workers to adhere to the program. For example, if broadcasters develop a policy that relies on personal monitoring devices, broadcasters must train users on the application and limitations of these devices. (A personal monitor is a beeper-sized, belt-worn device that alerts the wearer when he or she enters an area in which RF is present above a predefined level.) The key elements of a health-and-safety program are discussed later in this article.

The OSHA website and the NAB handbook (discussed later) give specific guidelines and information regarding content and actions broadcasters can use to develop an OSHA-compliant health-and-safety policy. Visit the OSHA website at www.osha-slc.gov/SLTC/radiofrequencyradiation for detailed information and examples on developing procedures and documentation for OSHA compliance efforts. Additionally, the IEEE has a group called SCC 28 that is responsible for developing NIR exposure standards. Within SCC 28, working group 4 is preparing a detailed document that will address procedures and documentation, and help to define responsibilities for compliance. When released next year, the document should also provide many additional practical resources.

Complying with the “letter of the law” (the FCC rules) alone can be rather simple. However, complying with the intent of the rules is just as important and should be a primary concern to employers and operators of broadcast facilities. The intent of the rules becomes clear when broadcasters ask themselves, “What needs to be done to ensure worker safety?” This is where the difference between meeting the minimum requirements of an FCC rule and true worker safety begins.

Consider going further than the minimum requirements necessary to achieve compliance. For example, all broadcasters are comfortable with the idea that an interlock on the transmitter door can prevent harm. Yet many broadcasters rely on a remote operator to deactivate the main transmit antenna, preventing the on-site tower workers from reducing power to the main transmitter. Obviously, while this procedure may be consistent with FCC and OSHA rules, it would not take much effort on the part of the broadcaster to go beyond the minimum requirements and provide a mechanism for an authorized person at the transmitter site to de-energize the transmitter or antenna, and prevent a remote operator from re-energizing it until the site is vacated.

FCC issues

The FCC has re-committed itself to enforcement of its rules. Jerry Ulcek, one of the writers of OET65, is currently leading an effort within the FCC’s Enforcement Bureau to develop inspection standards and educate enforcement personnel with respect to non-ionizing-radiation topics. Several of the conclusions reached through this effort are important to keep in mind when writing and deploying a health-and-safety plan.

  • Control access to the site. Broadcasters must be careful that access to a site is truly controlled. For example, fences around sites that are supposed to be closed actually need to be. We have all seen fences around the base of AM towers that are falling down, have had boards knocked out of them, or are left open. If the site is not “properly controlled,” the FCC will enforce the general-public exposure standards (these are the lower of the two tiers of exposure –see OET65 for a full discussion of “occupational” and “general-public” exposure standards).
  • Those who do access a controlled area must have the proper training. People who have not had a chance to ask questions about the situation and do not have a complete understanding of the signage have not had proper training and do not meet the condition of being “occupational” (occupational people can access areas of great RF energy, due to their knowledge and training). Posted signs with particular industry-specific information may be perfectly clear to those in the industry, but may be vague or confusing to others. For example, a common compliance action is to limit the time an individual can stay in a particular area. Imagine the possible interpretations f a sign that simply says “three-minute exposure limit.” To a properly trained person, that sign would be perfectly clear. But, to just about anyone else, it might raise questions such as, “Does that mean three minutes a day?” “Does it mean three minutes an hour?”
  • Even if people are prevented from accessing areas that are perfectly safe, many people become overly concerned about RF exposure due to a lack of basic knowledge. A fairly small amount of information and educational material can go a long way toward preventing unnecessary alarm or concern. Consider making some basic educational material available to anyone who wants it, not just those who need it.
  • Generally, most of us would consider “professionals” to be occupational, and allow them access to areas that might have higher-tier, occupational exposure levels. Electrical contractors, phone repair/installation personnel and other contractors are mistakenly assumed to be occupational persons and thus improperly are allowed access to areas that exceed general-public exposure limits. Unless a person has met all of the conditions to be categorized as occupational, he or she is not occupational and must be protected to the general-public standards. This situation most often occurs at mountaintop sites, rooftop sites and AM stations. There are few contractors who climb towers who are not in the industry and who have not met the conditions to be considered occupational. Trade associations such as the National Association of Tower Erectors promote tower rigger safety, including RF awareness training. Broadcasters should always make sure that subcontractors supply persons appropriately trained for the RF environment in which they will work.
  • In multiple-licensee situations (antenna “farms”), there are few sites that have effective power-down agreements. Where multiple transmitting antennas are co-located, it is important to have agreements with the other licensees regarding times or windows in which one licensee can ask the others to reduce power so that maintenance operations can be performed safely. In densely-located broadcast sites, the RF energy from one station’s facilities can be at or above the safe limits at a neighboring site or tower. Thus, one broadcaster may not be able to have someone safely climb a tower or work on an antenna without the cooperation of another licensee. The author has heard many anecdotal stories of tower climbers who are told, “Just get it done, regardless of safety.” Too often, the cost of a delay associated with reducing power is considered too high. So, rather than rescheduling maintenance at a time convenient to all parties, climbers have been “incentivized.” This situation can be eliminated through proper multi-user agreements, clearly defining the responsibilities of all parties.
  • The RF Worksheets Appendix to FCC Form 301 helps broadcasters assess their level of compliance, step by step. The FCC forms are available on its Web site at http://www.fcc.gov/formpage.html. But, simply completing the worksheet and stating that there are no publicly accessible areas that exceed general-population exposure limits is certainly not the end of a broadcaster’s compliance responsibilities. The facility must maintain ongoing compliance – forever. A broadcaster’s obligations under FCC and OSHA rules and regulations just begin when he signs Form 301. Routine review of work practices and updating exposure calculations with changes to the RF environment are paramount to maintaining ongoing compliance.
  • Currently, the FCC rules do not include specific protection guidelines or limits for RF shock and burn. At the time the rules were developed, the equipment for measuring induced and contact currents were not as readily available as they are now. While no time line exists for adding limits to the standards, such limits will be included at some point in the future.
  • Enforcement Bureau Field Activities – at this time, FCC employees are being trained to deploy additional enforcement of guidelines nationwide. This training is occurring not just at the Colorado office, or the Washington, DC or Gettysburg, PA headquarters – all FCC Enforcement Bureau personnel are being trained on non-ionizing radiation rules and regulations. In the very near future, when the FCC inspects broadcasters, its questions will address radiation as well as the public-inspection file and tower lighting.
  • OSHA issuesMr. Richard Strickland of NARDA Microwave wrote "Key Elements of a Safety Program for Broadcasters," part of the NAB “A Broadcaster’s Guide to FCC RF Radiation Regulations Compliance” (Item #3859, available at http://www.nab.org/nabstore. This document details 11 key elements of a health-and-safety program, which are summarized below. While these 11 elements are not official OSHA elements, they have earned general industry acceptance. If implemented, they can help any broadcaster become OSHA compliant.Written documentation of the program. If it isn’t written, broadcasters do not have a safety program.Management support. A safety program must have the full backing of management and must commit to and allocate the appropriate resources.Education and communication. The safety program must be communicated to the broadcaster’s employees, who must understand the work rules, procedures and policies they are expected to follow. Education is an ongoing requirement. Initial training is required when the safety program is first put in place, and periodic refresher training is also required.Enforcement. As an employer, broadcasters must enforce the safety program. It is up to the broadcaster to make sure that its employees are following the program.Identification of hazard areas. Broadcasters must have a reasonable idea where the field strengths may exceed the Maximum Permissible Exposure (“MPE”) (see OET 65 for a complete discussion of MPE) levels for both occupational/controlled areas and for general-population/uncontrolled areas. This requires periodic surveillance by a competent person who can effectively assess hazard levels.Marking and control of hazard areas. Once a broadcaster has determined potential hazard areas through calculations or measurements, it must identify such areas to those who would have access. Broadcasters often accomplish this by posting appropriate signs.Controls and/or work practices. Establish work practices. Mr. Strickland’s document highly recommends that broadcasters establish boundaries that do not depend on time averaging. It is risky to depend on human behavior, for example, when allowing an individual to work in a certain area for three minutes because the field levels are 200 percent of the MPE. Multiple-site operators should consider adding site-specific work rules to the corporate-level safety program.Employee involvement. Employees must understand the rules and procedures of the safety program, and a program’s procedures must incorporate practical, efficient working considerations. The program must not be unduly impractical for someone to accomplish his or her job.Medical program. First, employees who are expected to work in areas with potential exposure to RF fields above a modest level should be screened to identify those with medical implants that contain electronic circuitry. Second, the safety program must have provisions to handle overexposure incidents, whether real or unsubstantiated. Severe situations will require a physical exam. All incidents should be documented using a standard form that helps broadcasters quantify and record the level of the exposure. Often, a reported overexposure incident is found to be fully within the FCC regulations once the elements of whole-body averaging and time averaging are considered.Scheduled reviews. Broadcasters should review their safety programs annually so that deficiencies can be identified and resolved.Assignment of responsibility. A broadcaster must clearly identify someone in its organization as the RF safety person. This individual, who will have other duties as well, must have the necessary authority and resources to implement and enforce all aspects of the safety program.A broadcaster’s obligations to human health and safety do not end with FCC certification – they begin there.Richard P. Biby is a professional engineer and chief technology officer of Sitesafe Inc.