Step by Step Guide to Electromagnetic Field Surveys - a Recommended EMF Measurement Procedure
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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.
Green links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved. Author Daniel Friedman.
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. Steps of a detailed procedure for making accurate EMF electromagnetic field strength measurements & surveys; Recommended EMF measurement procedures for repeatability in the field; Recommended documentation when measuring electromagnetic fields at propertie
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. See Recommended EMF Measurement Procedure for details of how to collect EMF measurement data.
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.
Please do not contact us with a request buy EMF or RF measuring equipment. We do not sell anything. To do so would be a conflict of interest for this website. These devices are readily available from many electrical equipment and home inspection equipment suppliers. 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.
Outside Measurements of Electromagnetic Field Strength at a Property
 Make these EMF measurements
- At perimeter of the property at a point closest to a suspect source such as a power transmission or distribution
line
- 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.
- At targets of opportunity such as pole-transformers near building, below service laterals to building. (Photo at left)
- 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)
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Document these Outdoor EMF measurement Parameters and Readings
- Estimated or measured distance from nearest point on building to point directly below nearby power line
- Same, for distance from corners of building to the point named above.
- The date and time of the EMF measurement, for comparison with power transmission line load level data for that same time.
- The EMF levels found at each location
Indoor Measurements of Electromagnetic Fields
If 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.
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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.
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Other indoor targets of opportunity in residential properties
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- 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.
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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
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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.
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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.
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
Reply:
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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Technical Reviewers & References
Related Topics, found near the top of this page suggest articles closely related to this one.
- Electric Power Lines, Electromagnetic Fields, Cancer Risk,
& "Enviro-Scare" - The Normal Curve Cycle of Public Fear About Environmental Issues - online document by DF
- A Procedure for Measuring EMF electromagnetic fields online document by DF
- "Questions and Answers about Biological Effects and Potential Hazards of Radiofrequency Electromagnetic Fields", Federal Communications Commission, Office of Engineering and Technology, US FCC, OET Bulleting 56, 4th Edition, August 1999
" Many consumer and industrial products and applications make use of some form of
electromagnetic energy. One type of electromagnetic energy that is of increasing importance
worldwide is radiofrequency (or "RF") energy, including radio waves and microwaves, which
is used for providing telecommunications, broadcast and other services. In the United States
the Federal Communications Commission (FCC) authorizes or licenses most RF
telecommunications services, facilities, and devices used by the public, industry and state and
local governmental organizations. Because of its regulatory responsibilities in this area the
FCC often receives inquiries concerning whether there are potential safety hazards due to
human exposure to RF energy emitted by FCC-regulated transmitters. Heightened awareness
of the expanding use of RF technology has led some people to speculate that "electromagnetic
pollution" is causing significant risks to human health from environmental RF electromagnetic
fields. This document is designed to provide factual information and to answer some of the
most commonly asked questions related to this topic." - original source: U.S. Federal Communications Commission Office of Engineering and Technology, http://www.fcc.gov/Bureaus/Engineering_Technology/Documents/bulletins/oet56/oet56e4.pdf
- "Magnetic Field Exposure and Cancer: Questions and Answers [ copy on file as /emf/EMF_Fact_Sheet_NCI_NIH.pdf ] - ," National Cancer Institute, U.S. National Institutes of Health, web search September 2010, original source: http://www.cancer.gov/cancertopics/factsheet/Risk/magnetic-fields
makes these five key points about EMF
- Electric and magnetic fields (EMF) are areas of energy that surround any electrical device. EMFs are produced by power lines, electrical wiring, and appliances (see Question 1).
- Electric fields are easily shielded or weakened by walls and other objects, whereas magnetic fields are not. Since magnetic fields are more likely to penetrate the body, they are the component of EMFs that are usually studied in relation to cancer (see Question 1).
- Overall, there is limited evidence that magnetic fields cause childhood leukemia, and there is inadequate evidence that these magnetic fields cause other cancers in children (see Question 2).
- Studies of magnetic field exposure from power lines and electric blankets in adults show little evidence of an association with leukemia, brain tumors, or breast cancer (see Question 3).
- Past studies of occupational magnetic field exposure in adults showed very small increases in leukemia and brain tumors. However, more recent, well-conducted studies have shown inconsistent associations with leukemia, brain tumors, and breast cancer (see Question 4).
- EMF RF FIELD & FREQUENCY DEFINITIONS RF and EMF measurement tools need to be properly chosen to measure the particular type and frequency of RF or EMF signal that is of interest. See EMF RF FIELD & FREQUENCY DEFINITIONS for a simple explanation of different types of radio frequency (RF) and electromagnetic frequency (EMF) types and where they are found.
- Definitions of Gauss vs Milligauss for details about gauss and milligauss and definitions of these terms.
- Consumer Product Safety Commission, 800-638-CPSC.
- US Environmental Protection Agency, Office of Pesticides
and Toxic Substances, TSCA Assistance Office (TS-799), 800-424-9065
or 202-554-1404.
- "Evaluation of Potential Carcinogenicity of Electromagnetic Fields,"
EPA Report #EPA/600/6-90/005B October 1990. EPA: 513/569-7562.
- "Biological Effects of Power Frequency Electric and Magnetic Fields"
background paper, prepared as part of OTA's assessment of "Electric Power
Wheeling and Dealing: Technological Considerations for Increasing Competition,"
prepared for OTA by Indira Nair, M. Granger Morgan, H. Keith Florig, Department
of Engineering and Public Policy, Carnegie Mellon University, Pittsburgh, PA
15213
- "Biological Effects of Power Line Fields," New York State Powerline
Project. Scientific Advisory Board Final Report, July 1, 1987.
- "Extremely Low Frequency (ELF) Fields," Environmental Health
Criteria 35. World Health Organization, Geneva, 1984.
- "Electric and Magnetic Fields at Extremely Low Frequencies:
Interactions with Biological Systems. In: Non ionizing Radiation Protection,
World Health Organization, Regional Office for Europe, Copenhagen, 1987.
- "Electric and Magnetic Fields from 60 Hertz Electric Power: What do
we know about possible health risks?," Department of Engineering and Public
Policy, Carnegie Mellon University, Pittsburgh, PA 15213 1989.
- "Electromagnetic Fields Are Being Scrutinized for Linkage to
Cancer," Sandra Blakeslee, New York Times, Medical Science section, April
2, 1991
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
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