8.2 THE PURPOSE OF RF SAFETY ASSESSMENT
The purpose of an RF safety assessment is to determine the exposure associated with an RF source under specified conditions and to establish whether that exposure complies with the applicable RF exposure standard. A defensible assessment identifies the applicable standard and exposure category, the relevant limits and averaging conditions, the source configuration, and the people or locations represented by the assessment. It must also document the methods, assumptions, uncertainties, and operating conditions on which the compliance conclusion is based.
Compliance may be demonstrated using either reference levels or basic restrictions. Reference levels are expressed using quantities that can generally be measured or calculated outside the body, such as electric-field strength, magnetic-field strength, and incident power density. Because reference levels are derived conservatively from the basic restrictions, compliance with an applicable reference level demonstrates compliance with the corresponding basic restriction.
Exceeding a reference level does not necessarily mean that a basic restriction has been exceeded or that the exposure is unsafe. It indicates that a more detailed assessment may be required. Where reference levels are exceeded or are not applicable to the exposure conditions, compliance may instead be demonstrated by determining the relevant internal or surface quantities, such as induced electric field, specific absorption rate (SAR), or absorbed power density. These quantities may be determined using standardized laboratory measurements, analytical calculations, or validated computational models.
An RF safety assessment may therefore use source-based exclusion criteria, conservative analytical calculations, direct field measurements, standardized laboratory procedures, numerical computation, or an appropriate combination of these methods. The preferred approach is normally the least complex method capable of providing a valid and sufficiently conservative compliance decision. More detailed methods are required when a simpler assessment cannot demonstrate compliance with adequate confidence.
Measurement and computation should consequently be regarded as complementary techniques. Whatever method is selected, the assessment must account for relevant operating conditions, spatial and temporal variation, simultaneous sources, applicable averaging requirements, and assessment uncertainty. Its conclusion applies to the source configuration and exposure scenario that were assessed; it should not be treated as an unrestricted statement about every possible operating condition.