D.5 DOMESTIC RF SOURCES
Induction cooking. Domestic induction cooktops normally operate at frequencies of approximately 20–100 kHz. A single cooking zone commonly draws about 1–3.7 kW of electrical power, while a multi-zone cooktop may have a total connected load of roughly 3–11 kW. Booster modes temporarily apply greater power to one zone, often by sharing the available supply among zones. The electrical input or heating rating should not be interpreted as radiated RF power: most energy is magnetically coupled into the ferromagnetic cookware and converted to heat. Leakage magnetic fields are greatest close to the energized coil and may increase when cookware is undersized, off-center, unsuitable, or absent. Exposure decreases rapidly with distance, so normal operating position, correct pan placement, and compliance with manufacturer guidance are important—particularly for users of implanted electronic medical devices.
Microwave ovens. Household microwave ovens usually operate at approximately 2.45 GHz and commonly deliver about 500–1,200 W of microwave power into the oven cavity; their electrical input is higher because the magnetron or solid-state source and supporting circuits are not perfectly efficient. The cavity and door screen are designed to contain the field and opening the door interrupts microwave generation. The relevant external exposure is therefore leakage rather than the rated cooking power. In the United States, the product standard limits leakage to 1 mW cm–² at manufacture and 5 mW cm–² during the oven’s service life, measured 5 cm from the surface; properly maintained ovens normally produce levels well below this limit. Damaged doors, seals, hinges, or interlocks should not be used.
Smart devices. The term covers a wide range of connected domestic equipment, including smart speakers, televisions, security cameras, thermostats, appliances, lighting controllers, sensors, and hubs. Wi-Fi transmitters commonly operate in the 2.4, 5, or 6 GHz bands with conducted outputs ranging from a few tens of milliwatts in small battery-powered products to several hundred milliwatts in access points; permitted EIRP can approach 1 W or more for some device classes and jurisdictions. Bluetooth and Zigbee radios usually operate at about 1–20 mW, although selected higher-power products may reach 100 mW. Low-power sensors may transmit only intermittently at milliwatt or sub-milliwatt levels. Actual time-averaged emission is normally far below the maximum rating because many devices send short packets, remain in receive or sleep mode for most of the time, and use adaptive power control. A mains-powered Wi-Fi camera or streaming device may transmit more frequently than a battery-operated door sensor, so technology, data traffic, duty cycle, antenna gain, and separation distance are all more informative than a single nominal power figure.