Step by Step Guide to Electromagnetic Field Surveys - a Recommended EMF Measurement Procedure

Outside Measurements of Electromagnetic Field Strength at a Property

Make these Standard EMF Outdoor 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)

How to make a DIY test for EMF at house near a power line

An InspectApedia reader asked us:

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

Answer:

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, 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.

Details are at ENVIRO-SCARE - PUBLIC FEAR CYCLES

There is ample data including in some of our articles, on the relationship between field strength and distance from the source

see EMF MEASUREMENT DISTANCE 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.

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.

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

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.

Toasters, coffee makers, electric irons, microwave ovens, 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 EMF Measurement Targets of opportunity in residential properties

• 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 above).
• 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.
• Watch for EMF Traced to Electrical Wiring Errors!

  An inspectApedia reader with experience in field measurement of electromagnetic fields commented:

  Hi, I will just add to your description of magnetic field sources, that in my decades of field surveys in buildings, the main source of area magnetic fields comes from certain common wiring errors which shunt neutral current from one circuit off to either grounding conductors, pipes, ducts, girders, etc or else to neutral conductors from other circuits.

  The result is net current fields, which weaken only directly with distance.

  These are NEC Code violations and can be corrected by electricians who are shown where the error is. For details see my book, Tracing EMFs in Building Wiring and Grounding. - Karl Riley (Aug 16, 2012)

Commercial / industrial 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

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.

Commercial / Industrial 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.