Photograph of an electric meter too close to a bed and sleeping area - high EMF will be measured if quite close to electrical meters Step by Step Guide to Electromagnetic Field Surveys - a Recommended EMF Measurement Procedure

  • EMF MEASUREMENT STEP BY STEP - CONTENTS: details of how to make reliable measurements of electromagnetic field exposure: EMF levels using simple hand-held inexpensive instruments. Outside EMF Measurements & Outside EMF Measurement Documentation. Indoor EMF Measurements. Other Indoor EMF Measurement Targets. Workplace EMF Measurements. EMF Measurement Documentation Details
  • POST a QUESTION or READ FAQs about how to measure electromagnetic fields, EMF radiation at and around buildings

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EMF exposure field strength measurements, exact procedure: this paper discusses a recommended procedure for performing electromagnetic field (EMF) or electro-magnetic radiation EMR measurements either by engaging a professional or by consumers using low-cost instruments which measure EMF exposure levels in gauss or milligauss.

We discusses sources of error and variation in EMF measurements and we review and make suggestions for using several low-cost EMF measurement devices to determine the instantaneous electromagnetic field exposure.

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Steps in A Recommended Electromagnetic Field Measurement Procedure - How to make Outdoor & Indoor EMF Measurements

We have documented a proposed procedure for making site surveys of electromagnetic field strength in order to improve the accuracy and repeatability of such measurements. We welcome critique and suggestions for this procedure. Contact Us with criticism.

Article Contents

As we explained earlier:

Instead of contacting us with a request to perform EMF Electromagnetic or RF Radio Frequency Field Strength measurements, in most cases it is more economical and convenient for a property owner to purchase their own instrument, making measurements under varying conditions.

In this series of articles we describe how to make measurements using a consistent approach and using good documentation. Following good procedure and using instruments properly are two steps towards making accurate, repeatable EMF measurements.

But because the signal transmission for RF sources such as radio, TV, or cell towers, the load on a power transmission line is not under control of an individual property owner, and because the EMF strength varies as the power transmission line load varies, it is important to have an idea of that condition as well when attempting to characterize EMF exposure at a specific location.

In contrast, EMF measurements are quite accurate and repeatable at other EMF sources such as close to electrical appliances and service entry cables.

Outside Measurements of Electromagnetic Field Strength at a Property

Electrical power transformer on a utility pole in the U.S.  (C) Daniel FriedmanMake these EMF measurements

  1. At perimeter of the property at a point closest to a suspect source such as a power transmission or distribution line
  2. At the electric meter at distance of 12" (confirms equipment is responding). Also note if the electric meter or service entry cable of other high amperage wiring is run along walls on the other side of which may be found the head of beds in sleeping areas.
  3. At targets of opportunity such as pole-transformers near building, below service laterals to building. (Photo at left)
  4. In street in front of building, or other apparently neutral location more than 1000 meters from the power line of interest, to determine an apparent ambient or background level (commonly 0 to .5 mG, larger near local power distribution wiring under some conditions)

Document these Outdoor EMF measurement Parameters and Readings

  1. Estimated or measured distance from nearest point on building to point directly below nearby power line
  2. Same, for distance from corners of building to the point named above.
  3. The date and time of the EMF measurement, for comparison with power transmission line load level data for that same time.
  4. The EMF levels found at each location

Indoor Measurements of Electromagnetic Fields

Electrical appliances toaster coffee maker (C) Daniel FriedmanIf the outside of the building is in a strong EMF, all measurements inside the building might be expected to produce the identical number.

However if the inspector agrees to a detailed site survey we recommend spot checks in every room as well as at obvious common interior targets of interest (such as an electrical device which is normally kept on and which is close to the head of a bed (clocks).

You will observe that while there may be a strong field close to a clock, the field will fall off to undetectable in 2 feet or so.

Toasters, coffee makers, electric irons, crockpots, and similar electrical appliances are an EMF Enviro-Scare "red-herring" and need not be measured unless the client indicates that someone sleeps with their head in or on the toaster and that it's kept on for long periods of time each day.

Other indoor targets of opportunity in residential properties

Photograph of an electric meter too close to a bed and sleeping area - high EMF will be measured if quite close to electrical meters (C) Daniel Friedman

  • Bedroom walls adjacent to electrical service equipment, refrigerators, or computers if left on 24 hours.
  • Bedroom walls or bed locations on the opposite side of walls where electrical meters or service entry cable wiring are run (photo at left).
  • Appliances that are always-on. Some electric clocks, located on a night-stand close to a sleeper's head will expose the occupant to a much stronger EMF than nearby power lines.
  • Bedroom walls inside of outside location of electrical service entrance cables.
  • Every bedroom heated by electric radiant panels in ceiling or floor (when these devices or systems are turned on) - we have found very strange anomalies in some rooms, possibly due to damaged equipment or improperly installed wiring. we have also identified sections of floor or ceiling electric radiant heat that was no longer operating. (You can also make that check with the heat on using an infra red sensor or thermography.
  • Sleeping areas (or areas where people spend many hours daily) traversed by steel piping or ducting which in turn passes by electrical equipment.

Commercial properties have special targets of opportunity for EMF Measurements:

Local power distribution systems, electric meter buses which may produce a field which is further distributed by building plumbing or wiring

Special high-amp equipment such as X-ray machines, computer equipment, compressors

Gauss meter setting (C) Daniel Friedman

Given the ease with which electrical components within a building can be relocated or modified, field inspectors are strongly warned to absolutely refuse to permit clients to assert that the sample measurements made are a comprehensive or exhaustive study of a property.

Health professionals, epidemiological experts, and in the case of EMF, electrical engineers can offer competent, expert advice which should be considered before any costly or risky actions are taken regarding this or other environmental topics.

This information is has not been sanctioned nor technically reviewed by the American Society of Home Inspectors.

Use it at your own risk.

EMF Measurement Documentation Requirements

Document date, time, location, weather conditions (hot means air conditioners are running and load may be higher; time means it is at least theoretically possible to correlate the measurement results with actual load data if the power company would provide it)

Document distance from measurement location to suspected source of EMF and identify that source

Document any reports of medical anomalies (if anyone volunteers such information or if your procedure or study permits its collection)

See WORKPLACE EXPOSURE to Electromagnetic Fields for information about exposure to electromagnetic fields in the workplace.

Please see WORKSHEET for EMF MEASUREMENTS - Example for a sample worksheet that collects EMF measurements and summarizes the results.

Readers are urged to consult expert sources and to give any suggestions regarding these notes to the author. Readers may want to see our EXCEL Spreadsheet EMS_Survey_Sample1.xls for an example of common locations and measurement points. This spread sheet includes computations necessary to produce mathematically valid measurement results for those who are using position-sensitive instruments.

Some studies by some experts have suggested a possible link between exposure to electromagnetic fields and various cancers or other health problems. Other studies suggest that no definite correlation could be demonstrated. It is likely that the jury will be out on this matter for some time, for both economic and political reasons.

Small absolute health risk from EMF: Most researchers indicate that where a risk is present, the absolute risk level from EMF is likely to be small, and less than other less obscure hazards. (Automobile accidents, trip and fall, fire, and shock hazards, smoking and other health risks.) Consumers should not let focus on a specific emotionally-charged hazard distract them from these other more mundane but more dangerous concerns.

Instead of contacting us with a request to perform EMF Electromagnetic or RF Radio Frequency Field Strength measurements, in most cases it is more economical and convenient for a property owner to purchase their own instrument, making measurements under varying conditions.

See Recommended EMF Measurement Procedure for details of how to collect EMF measurement data.

See Evaluation of Low-Cost EMF Instruments This article describes several low-cost and reasonably accurate EMF measurement devices that are readily available.

See Radio Frequency RF Detection Meters This article describes several low-cost and accurate radio frequency or RF detection and measurement devices suitable for radio, TV, cellphone, microwave, and similar signals.


Continue reading at EMF SURVEY PROCEDURE or select a topic from the More Reading links shown below.


Suggested citation for this web page

EMF MEASUREMENT STEP BY STEP at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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Frequently Asked Questions (FAQs)

Question: information on how I can test a house for electromagnetic waves

I'm considering buying a house next to high tension wires please help me with information on how I can test the house for electromagnetic waves. - F.R. 6/1/2013


A competent onsite inspection by an expert usually finds a range of hazards, some of which may be more immediate and severe than possible risks from electromagnetic fields, so be sure you aren't distracted from those. That said, here are some things to consider:

You can probably buy a decent quality EMF/EMR meter and make your own field measurements for a fraction of the cost of bringing in a hired professional, with the added advantage of making multiple measurements since over time field strengths vary considerably depending on the load on the power line.

You can eschew measurement entirely and still estimate both the possible impact on real estate re-sale (price or time on market due to some buyers' fear level) and possible exposure levels to EMF, independent of any actual health risk assessment (ENVIRO-SCARE - PUBLIC FEAR CYCLES ) , by determining the name, owner, and transmission line voltage levels of the power lines near your building along with simple on-the-ground measurements of the distances involved.

There is ample data including in some of our articles, on the relationship between field strength and distance from the source (Distance from the EMF Source Affects Strength). Since actual electrical field strength varies with load on the power line, knowing the line's maximum-rated voltage level can set an upper limit of field strengths regardless of individual onsite measurements.

At EMF MEASUREMENT BASICS we introduce the topic and outline measurement procedures; that article includes links to detailed how-to procedures, worksheets, and related data.

At EMF MEASUREMENT STEP BY STEP  we give detailed measurement suggestions.

If any of our articles leave you with questions, comments, criticism, just let me know and I'll do my best to research further as needed.                                            


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