RF Signs of the Times—Part Two
Part One of this series summarized the FCC’s long-pending proceeding and initial set of decisions on human exposure to radiofrequency (RF) fields. Generally, the more complicated and difficult decisions were deferred. In light of Chairman Pai’s commitments to Congress, we expect the FCC to resolve at least some of the remaining issues in 2018. Let us now examine areas that are likely up next for decision.
In addition to the decisions in its First Report and Order (R&O), the FCC adopted a Further Notice of Proposed Rulemaking (FNPRM) and Notice of Inquiry (NOI). The FCC summarized the FNPRM as follows:
We are proposing to broadly revise and harmonize the criteria for determining whether single or multiple fixed, mobile, or portable RF sources are subject to routine evaluation for compliance with the RF exposure limits or are exempted from such evaluations. Additionally, we propose clarifications of evaluation requirements for portable and medical implant devices. We also propose to adopt specific new requirements for signs and barriers at fixed transmitter sites to ensure compliance with public and occupational exposure limits. Further, we propose a clarification of the definition of transient exposure for non-workers exposed at levels up to occupational limits.
[We] propose establishing general exemptions from evaluation to determine compliance in place of existing service-specific “categorical exclusions.” These proposed exemptions involve simple calculations to establish whether any further determination of compliance is necessary. . . . The new, general exemptions would instead apply to all subparts authorizing RF sources. . . . Given the trend toward opportunistic spectrum access to allow services to utilize multiple bands of frequencies with various power limits, inclusion of all services is necessary to better ensure compliance with our exposure limits.
Important proposed changes in the FNPRM include:
- Clarified definitions of “power” for consistency throughout the Rules.
- Changes to general exemption criteria based on power, distance, and frequencies involved for all services using fixed, mobile, and portable transmitters including implants; elimination of distinctions between different services.
- A blanket exemption for single transmitter operations with up to 1 milliwatt (mW) available maximum time-averaged power independent of frequency and service; minimum two-centimeter separation between multiple transmitters operation at up to 1 mW.
- For single transmitter operation above 1 mW, requiring routine environmental evaluation above a “sliding scale” of values for minimum distance as a function of wavelength and maximum power as a function of frequency and distance for five frequency ranges from 0.3-100,000 MHz. The FNPRM acknowledges that the formulas used for the sliding scale are based on worst-case calculations but states that they trigger further evaluation, not necessarily a finding of non-compliance with permitted exposure limits.
- A multi-step equation to sum the effect of multiple fixed transmissions in proximity to each other and determine whether further evaluation is required.
- Additional exemption criteria based primarily on Specific Absorption Rate (SAR) limits for single fixed, mobile, and portable transmitters in the frequency range 300 MHz-6 GHz at distances of 0.5-40 centimeters from a human body and formulas to determine whether additional evaluation is required for multiple portable and multiple portable and mobile transmitters.
The FNPRM also proposes changes regarding mitigation of exposure to RF, stating that “. . . mitigation matters involve post-evaluation procedures to ensure that our exposure limits are not exceeded. Such measures include labels, signs, barriers, occupational training, and enforcement.” Specifically, these proposals include:
- Clarification of transient exposure and how to apply exposure limits in controlled environments with respect to averaging time.
- Specific new training, access restriction, and signage requirements for fixed transmitter sites with a new four-category system based on an Institute of Electrical and Electronics Engineers (IEEE) standard.
There are four-categories of proposed signage requirements. Signage would be required for Categories 2-4 but optional for Category 1.
Category 1 is exposure up to the General Population (GP) limit. No signage would be required. Green “INFORMATION” signs stating that a transmitting source of RF energy is nearby but compliant with FCC exposure limits would be optional.
Category 2 is exposure above the GP limit and up to the Occupational (O) limit. Signs and access control would be required surrounding the area in which the GP limit is exceeded. Blue “NOTICE” signs would have to be large enough to be visible at the separation distance required to comply with the GP limit. Training would be required for occupational personnel with access to the area. Use of personal RF monitors would be recommended but not required.
Category 3 is exposure above the O limit and up to 10 times the O limit. In addition to the Category 2 mitigation requirements, yellow “CAUTION” signs would be required surrounding the area in which the O limit is exceeded. Transient individuals would not be permitted in the Category 3 area. Use of personal protective gear would be recommended but not required.
Category 4 is exposure to more than 10 times the O limit. In addition to the Category 3 mitigation requirements, orange “WARNING” signs would be required where the O limit could be exceeded by a factor of 10 and red “DANGER” signs would be required wherever immediate and serious injury would occur. If power reduction would not sufficiently protect in the event of human presence considering additional use of optional personal protective equipment, lockout/tagout procedures would have to be followed.
The signage for Categories 2, 3, and 4 would require inclusion of the “radiating antenna” RF energy advisory symbol, an explanation of the RF source, behavior necessary to comply with exposure limits, and contact information for a timely response in addition to the color and key words listed for each category.
The FNPRM states that barriers may not be appropriate for all Category 2 environments and that the FCC continues to support suggested Engineering and Technology (OET) exceptions not to require barriers in remote areas with unlikely public access. The FNPRM also reiterates the principle that licensees cannot exclusively on natural barriers for protection unless specifically approved by the FCC on a case-by-case basis. The FCC Enforcement Bureau can require corrective action and impose fines or other sanctions for non-compliance.