Electromagnetic Fields


Electrical devices and systems produce two different fields: an electric field like the one produced on the surface of a wool sweater on a dry winter day, and a magnetic field like the fields produced by a compass needle, a small magnet or the earth itself. These fields in combination are referred to as electromagnetic fields or EMF. EMF fields associated with electrical devices and appliances are produced only when the device is plugged in and operating. Devices which generate electromagnetic fields include radio or TV station transmitters, microwave ovens, power transmission lines, and electrical appliances.

Exposure to the very high intensity electromagnetic fields found in the immediate vicinity of certain sources such as radar installations and TV or radio transmitters can produce electrical shock or a variety of heating effects, which may range from a sensation of warmth to burns and eventual cataract formation.

Standards for permissible levels for occupational exposure to radio frequency radiation (from 300 kiloHertz to 100 gigaHertz) have been established by the New Jersey Department of Environmental Protection (NJDEP). NJDEP has also established regulations requiring that radio frequency and microwave heaters and sealers and industrial microwave ovens be registered. The federal government has established emission standards for the manufacturers of certain equipment, including televisions and video display terminals.

Microwave Ovens

EHS does not routinely survey household-type microwave ovens for leakage because properly operating ovens with intact doors and door seals do not produce excessive microwave leakage. EHS will survey any microwave oven upon request.

  • Keep the door seal area of a microwave oven clean and free of grease or food buildup to ensure a tight fit between the door and the oven.
  • Do not clean the door seal area with abrasive cleaners which can cause scratches or gouges and can cause microwave leakage.

Laboratory Microwave & RF Emitters

This section is under development and will be completed in the near future.  For questions about microwave and RF safety in the laboratory, contact the Radiation Safety Officer (see the Staff sidebar).


Princeton University has addressed radiofrequency (RF) radiation safety in research applications and has considered the impact of emissions from wireless technology on our general campus community.  For example, at our request, the New Jersey Department of Environmental Protection (NJDEP) in 2007 measured levels of RF radiation emitted by wireless networks on the Princeton University campus and determined that RF levels attributable to WiFi networks were generally not detectable or, when measured directly in contact with an access point antenna, were a very small fraction of federal, state and international guidelines or regulatory limits.  

Non-WiFi sources in the modern environment, such as mobile phones, are known to be much greater contributors to RF exposures than Wi-Fi networks.  Published exposure assessments, including direct measurements of transmitted power and computer modeling, indicate that the use of WiFi networks in any circumstance do not contribute in any significant way to RF exposure to bystanders.

Based on our recent and ongoing routine examination of literature on WiFi and health, there is no reason to believe that WiFi exposure on campus is a health hazard.  Princeton University will continue to monitor the scientific literature on this subject to determine whether additional reproducible, statistically valid, peer-reviewed, technically sound (e.g., with well-characterized dosimetry) studies provide evidence to the contrary.

Measurements at 60 Hz and Other Frequencies

EHS can make arrangements to monitor the 60 Hertz EMF fields associated with electrical appliances and the power distribution system.  If EHS does not have the capability to monitor EMF levels at other frequencies of interest, EHS will assist a department to obtain the services of an outside consultant.

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Colt Greer
Assistant Director and RSO

Chelsea McDonnell
Health and Safety Technician