The Numerical Assessment of RF Human Exposure to Microwave Ovens with Contact-Type Doors

Overview

In complex electromagnetic environments, cardiac pacemakers may be interfered with easily. Microwave ovens, as common household appliances, may display electromagnetic leakage, which may pose risks to pacemaker wearers. This work evaluates the electromagnetic exposure of pacemaker wearers under various conditions, including different distances from the microwave oven and varying oven door gap sizes. COMSOL Multiphysics was used to model a human thoracic cavity with a heart and unipolar pacemaker, as well as a microwave oven with contact-type doors.

Findings

• Specific Absorption Rate (SAR10g) and temperature increase in thoracic cavity and heart tissue:
  ● Inversely proportional to distance from the microwave source.
  ● Directly proportional to oven door gap size.
• Induced electric field intensity, temperature increase, and induced voltage in the pacemaker follow similar trends.
• Maximum SAR10g and temperature increase (at 100 mm distance, 0.3 mm door gap) in thoracic cavity and heart tissue were significantly below ICNIRP safety standards.
• The maximum induced voltage at the pacemaker electrode reached 5.322 mV, exceeding the sensitivity recommendation by ISO 14117 (2 mV) for unipolar pacemakers.
• Although direct threat to human health under normal conditions was not indicated, the voltage exceeds sensitivity thresholds that could influence pacemaker operation. This connection to potential interference and health risk should not be ignored.

Conclusion

• The electromagnetic radiation from microwave ovens with contact-type doors typically remains within established safety limits for tissue heating and electric field, but may still produce voltages high enough to trigger unipolar pacemakers improperly.
• The operation of a unipolar pacemaker may be affected if the user is within 300 mm of the microwave oven, particularly when device settings are at or below tested thresholds.
• Patients with pacemakers are strongly advised to maintain a safe distance, minimize exposure time, and consider device replacement or upgrading to bipolar pacemakers to reduce risk from electromagnetic fields.