8.11.4 Multiple Sources And Frequencies
Where more than one source or frequency contributes, the individual results must be combined using the summation rules in the applicable exposure standard. Raw electric-field strengths, magnetic-field strengths, or power densities should not simply be added unless the prescribed method explicitly requires that operation.
Different summations may apply to quantities associated with electrostimulation and thermal effects, and different temporal or spatial averaging requirements may apply across frequency ranges. A broadband screening result can be decisive when it is conservatively below the relevant criterion. Otherwise, frequency-selective measurement or source-specific calculation is needed to attribute and combine the contributions correctly.
8.11.5 Uncertainty And The Decision Rule
Uncertainty describes the dispersion reasonably attributable to the assessed value; it is not evidence that the result is incorrect. Its importance depends on the margin between the result and the applicable criterion, the conservatism of the method, and the decision rule required by the standard or regulatory authority.
A conservative screening result far below the criterion may support a clear conclusion with a proportionate uncertainty estimate rather than a highly detailed budget. As the result approaches the criterion, uncertainty and source variability become more important, and a more specific method or additional evidence may be required. The report should explain how uncertainty was included in the comparison.
If the available evidence cannot demonstrate compliance under the selected decision rule, the proper conclusion may be that the assessment is inconclusive and must be refined. That finding is not, by itself, proof that a basic restriction has been exceeded or that the exposure is unsafe.