The Dangers of Extension Cords
Extension Cord Concerns and Cautions
Electrical cords, including extension cords, have been involved in several electrical shock, overheating, and smoke/fire incidents in the DOE complex.
The typical contributor is damage that is visually apparent and which resulted from a single action:
Pictures 1 and 2: Abraded insulation and Pictures 3 and 4: Damage resulting from cord being
crimped grounding pin (loss of equipment crimped between the appliance and the wall
grounding) that resulted in electrical shocks). (incompatible plug configuration/receptacle orientation).
Extension cords present special concerns – concealed damage and improper use.
• Plug: damage to blades, pins and internal conductor connections.
• Receptacle: contacts no longer hold plugs securely, damage to internal conductor connections.
• Cord: broken conductor strands typically at but not limited to where the cord enters the plug or receptacle.
• Replaced, repaired or modified plug or receptacle: conductor connections inadequately secured.
• Connected to equipment that draws more power than the cord is rated for (i.e., major electrical loads such
as space heaters and other heating equipment, pumps
• Used in place of required permanent or temporary wiring.
All of the above can result in higher and possibly damaging
temperatures at the compromised locations and in the
remaining unbroken conductor strands. High temperatures
accelerate the aging process which can produce more of this
damage. Repeating this cycle can result in the damage from
a recent event shown in Picture 5.
Picture 5: Extension cord receptacle and
equipment plug damaged by overheating.
• Always inspect an extension cord before using it, every day it is in use, and when disconnecting it.
• Always grip the plug or receptacle, never the cord, when connecting or disconnecting.
Before using, verify:
• It is marked with the required UL or other approved agency tag (CE is not an approved agency).
• It is rated for the equipment it will supply power to. In almost all cases this means DO NOT use for high
power inductive loads such as space heaters and other heating equipment, pumps or motors.
• All visible parts are in good condition (e.g., intact insulation, no kinks, pins straight and undamaged, no
indication of overheating).
• The receptacle holds the equipment plug securely.
• It is routed where it will not be disturbed or a workplace obstacle/hazard.
Extension Cord Concerns and Cautions
LL-2018-LLNL-18 August 29, 2018 LLNL-POST-757569
• It is protected from foot and vehicle traffic and other hazards (e.g., pinch points and sharp edges) by protective devices and not contacting anything that may damage it.
• There will be slack and no sharp bends after connecting and the excess cord is not rolled up tightly.
• The equipment being powered is restrained from subsequent movement that could pinch or strain any cord (particularly important for equipment with motors, fans, pumps, or compressors that can vibrate or shimmy).
Check its temperature periodically during use. If it is getting hot, disconnect it and contact your safety representative.
If getting the cord repaired, make sure an Authority Having Jurisdiction inspects and approves the repair before the cord is returned to service. If the cord appears to have been repaired, be especially sensitive to the apparent condition of the replacement components and how secure they appear to be. When in doubt, have them re-verified.
Remember that an extension cord is a tool for a task and is to be disconnected when the task is finished.
• Your supervisor.
• Your organization’s Safety Manager, Electrical Safety Officer, ES&H representative or Facility Point of Contact.
• LLNL Electrical Safety Officer, Rich Green, (email@example.com, 925-422-5359).
• ES&H Manual, Document 16.1 Electrical Safety Program, Sections 3.8 and 3.9 at https://esh-int.llnl.gov/man/16.1.pdf
• Nationally Recognized Testing Laboratories at https://www.osha.gov/dts/otpca/nrtl/nrtllist.html.
• To search for other LLNL Lessons Learned, go to the "Lessons Learned" web site (https://cao-int.llnl.gov/lessons_learned/), select the topic of interest or click on "Search" and enter a keyword.
• Priority Descriptor: Yellow / Caution.
• Work/Function Categories (HSS entry): Conduct of Operations – Procedure Adherence.
• Hazard (HSS entry): Fire / Smoke / NFPA, Personal Injury / Exposure – Other.
• ISM Category (HSS entry): Analyze Hazards, Develop / Implement Controls, Perform Work.
• Keywords (HSS entry): electrical power cord, extension cord, overheating, permanent wiring, plug, receptacle, temporary wiring.
• Subject Category (LLNL LL web page): Electrical.