Biological Tissue Absorption from Wireless Devices
Wireless devices emit low-levels of radiation that are absorbed by biological tissues, when in close proximity. UL tests these devices to help ensure radio frequency exposure does not exceed mandated limits.
In recent years, wireless technology has dramatically improved to meet the need of the digital era. Users are often continuously connected to wireless devices, increasing data consumption. Higher bandwidth and frequency bands are needed to accommodate the data requirements of the average consumer.
Most mobile devices will be used within 20 cm of the user’s head, ankle, wrist or torso. At this proximity, the user is exposed to electromagnetic fields (EM Fields), or a low-level form of radiation. This is how wireless devices communicate. Exposure to these EM Fields may be of concern to the consumer.
Many countries across the globe have mandated requirements to address health and safety aspects for mobile devices. Manufacturers placing products on the market need to help ensure their mobile device complies with recommended guidelines for limiting exposure.
Many mobile devices with wireless capability that are operated within close proximity to the user are tested using a test method known as Specific Absorption Rate (SAR), which measures the amount of energy absorbed by biological tissue when using a wireless device over a period of time. SAR testing involves the use of a “phantom”, which simulates the human head. A liquid which is designed to be the electromagnetic equivalent of human tissue, or the human brain, is placed in this phantom. The device under test is put into a “phone call” at maximum power and a robotic arm then moves a measurement antenna through the liquids and makes EM Fields measurements.
SAR measurement tests for the most severe, worst-case and highest-power operating conditions for wireless devices. UL Certification means the device will never exceed the maximum levels, helping to protect the wearer from radiation levels at which adverse health effects may occur. At that point, devices can be more safely used and worn on the body for long periods of time.
For more information on SAR testing, visit: http://services.ul.com/service/sar-testing/