Even if you are only using approved electrical equipment and tools in the manner that they were designed, a basic understanding of electrical safety is needed. The information presented on this page is available to ensure that you have the adequate information to safely use electrical equipment. Electrical safety training resources and OSHA requirements for certified equipment are also provided below.
Factors Involved in Electrical Shock
One of the main hazards of using electrically powered equipment is electric shock, which happens when current flows through the body due to contact or close approach to exposed or faulty circuit parts. There are 3 primary factors that affect the severity of shock injury a person receives when he or she becomes part of an electrical circuit.
Current (amperes) is the killing factor in electrical shock, not the voltage. The voltage only determines how much current will flow through a given body resistance. In general, the body’s resistance to electrical shock is minimal, averaging approximately 10,000 Ohms (100,000 Ohms for dry skin to 1,000 Ohms if your skin is wet). At this resistance, even contact with standard 110-volt circuits can be lethal under certain conditions. Refer to the Physiological Effects table below.
OHMS LAW is Current (Amps) = Voltage (V) / Resistance (Ohms)
Hand-to-hand, hand- or head-to-foot, and ear-to-ear current paths are the most dangerous because it may cause severe damage to the heart, lungs, and brain. This is why it is important not to wear metal jewelry, not to lean against or use both hands-on electrical equipment so as not to become part of the circuit. Step potential is also a concern when the ground is electrified. Shuffle feet to keep them as close together as possible.
Here is a table that shows the physiological effect to your body from exposure to increasing levels of electric current. It also details approximately how much voltage is needed to achieve these current levels based on assumed body resistance (Average ~10,000 ohms).
Physiological Effects Table
Electric Current (1 second contact)
Physiological Effect
Voltage
1 mA
Threshold of feeling, tingling sensation.
10 V
5 mA
Accepted as maximum harmless current. Intense involuntary spasms might lead to other injury.
50 V
4-5 mA
Current as which a typical GFCI will trip.
Designed to protect you
10-30 mA
Beginning of sustained muscular contraction (“can’t let go” current).
100 V
75-300 mA
Ventricular fibrillation, fatal if continued.
750 V
15000 mA
Lowest current at which a typical fuse or circuit breaker trips.
Designed to protect equipment
Electrical Safety Training
For a comprehensive overview of basic electrical safety and things to consider while working with and around electricity and electrical equipment, EHS has developed an online course for Electrical Safety Awareness. This course can be found in the ATLAS Learning Center Course Catalog.
NOTE: If you plan to design, build or modify electrically powered equipment for your research you will need more advanced knowledge and training than is currently offered through MIT EHS. Please contact environment@mit.edu if you have questions related to more in-depth electrical training needs or have plans to build or modify electrical equipment.
Understand your limitations when using electrical equipment
Identify the hazards associated with electricity: shock, fire and arc flash
Recognize unsafe electrical conditions and equipment
Familiarization with information listed on equipment tags: NRTL, energy needs, load capacities
Describe basic safety controls and practices when working with electrical equipment
Identify electrical emergencies and explain how to respond to them
National Consensus Standards for Design and Installation
To safeguard against injury when using electrical equipment, requirements and standards have been established through the implementation of nationally recognized codes, approval tests, and electrical safety work practices. This is to ensure that you have adequate training and experience when handling electrical equipment.
National Electrical Code (NEC)® – supported by the NFPA provides electrical safety requirements for wiring methods used in the workplace, for live electric supply and communication lines and equipment for employees in the workplace.
Basic Electrical Safety
Only licensed electricians are permitted to work on building infrastructural electrical systems.
Should a circuit breaker or other protective device “trip”, ensure that a licensed electrician checks the circuit and equipment and corrects problems before resetting the breaker.
Report hazards (lack of protective guards or covers, damaged equipment, etc.) to the building manager, Department of Facilities, Environment, Health, and Safety Office, or supervisor immediately.
Discard any piece of equipment that gives you even the slightest shock. If the resistance through your body is lowered i.e. standing in water or touching metal, even the slightest shock can be deadly.
Take seriously any warning signs, barricades, or guards posted when electrical equipment is being repaired, installed, etc.
Junction boxes and electrical panels need to have proper covers in place to conceal all wiring. Hard wiring should not be exposed/accessible to non-electrical employees.
Do not leave electrical boxes, switch-gear, cabinets, or electrical rooms open when not directly attended.
Remove materials, especially those that are combustible, such as paper and wood from the area in front of electrical panels. There should be 36” of clearance for safe access if needed.
Do not operate electrical tools or equipment in wet areas or areas where potentially flammable dusts, vapors, or liquids are present unless specifically approved for the location.
De-energize equipment before removing any protective covers or guards.
Do not use an electrical outlet or switch if the protective cover is ajar, cracked, or missing.
Never put conductive metal objects into energized equipment.
Remove the cord from the outlet by pulling the plug instead of pulling on the cord.
Do not carry equipment by the cord – only by the handle or base.
Extension cords are used to temporarily operate electric equipment in areas where there are no outlets. Relocatable Power Taps (RPTs), more commonly known as power strips add extra outlet space, while a surge protector also defends against possible voltage spikes that could damage your electronic equipment. The following best practices should be followed when using these devices.
Re-route electrical cords or extension cords so they don’t run across the aisle/corridor or over pipes or through doors.
Be sure extension cords are properly rated for the job and used only temporarily.
Use extension cords with 3-prong plugs to ensure the equipment is grounded. Never remove the grounding post from a 3-prong plug so you can put it into a 2-prong.
Do not overload extension cords, multi-outlet strips or wall outlets.
All surge protectors or power strips need to be UL (Underwriters Laboratory) or ETL (Electrical Testing Laboratories) approved. Unlisted items may not have been tested for safety
Do not plug a surge protector, power strip or an extension cord into an existing surge protector, power strip or extension cord. This practice is called “daisy chaining” or “piggy backing” and can lead to serious problems.
There should only be one surge protector or power strip plugged into a single duplex electrical outlet.
Do not locate a surge protector, power strip or extension cord in any area where the unit would be covered with carpet, furniture, or any other item that will limit or prevent air circulation.
Do not staple, tack, or tape a surge protector or power strip.
Do not plug any equipment using over 5 Amps or 600 Watts into a power strip. This equipment should be plugged directly into a wall outlet.
Limit surge protector or power strip load to 80% of capacity listed on back label.
GFCIs are designed to protect people from electric shock.
A GFCI works by detecting a current drop from the hot to the neutral wiring in a circuit. When the GFCI senses approximately a 5ma difference it shuts down the circuit in 1/40 of a second.
GFCIs must be installed wherever a water hazard is present.
GFCIs can be at the breaker, the outlet, incorporated with the plug of the appliance/piece of equipment, or part of a short extension cord.
Example Images of GFCIs:
Wiring, Grounding, Insulation
All electrical installations or the replacement, modification, repair, or rehabilitation of any electrical installation must comply with the requirements of the National Electrical Code (NEC) of the National Fire Protection Association, and/or the U.S. Department of Labors’ Occupational Safety and Health Administration.
All equipment should be grounded and fused in accordance with NEC. All extension cords must have a grounding pin.
All electrical equipment should be properly insulated. Any power cords that are frayed must be discarded and any live/hot wires should be insulated to prevent danger of electrical shock.
Documents
The following documents are Standard Operating Procedures (SOPs) related to electrical safety. MIT certificate login is required to view the SOPs and can also be located under Forms/SOPs (keyword search: electrical).
Even if you are only using approved electrical equipment and tools in the manner that they were designed, a basic understanding of electrical safety is needed. The information presented on this page is available to ensure that you have the adequate information to safely use electrical equipment. Electrical safety training resources and OSHA requirements for certified equipment are also provided below.
Factors Involved in Electrical Shock
One of the main hazards of using electrically powered equipment is electric shock, which happens when current flows through the body due to contact or close approach to exposed or faulty circuit parts. There are 3 primary factors that affect the severity of shock injury a person receives when he or she becomes part of an electrical circuit.
Current (amperes) is the killing factor in electrical shock, not the voltage. The voltage only determines how much current will flow through a given body resistance. In general, the body’s resistance to electrical shock is minimal, averaging approximately 10,000 Ohms (100,000 Ohms for dry skin to 1,000 Ohms if your skin is wet). At this resistance, even contact with standard 110-volt circuits can be lethal under certain conditions. Refer to the Physiological Effects table below.
OHMS LAW is Current (Amps) = Voltage (V) / Resistance (Ohms)
Hand-to-hand, hand- or head-to-foot, and ear-to-ear current paths are the most dangerous because it may cause severe damage to the heart, lungs, and brain. This is why it is important not to wear metal jewelry, not to lean against or use both hands-on electrical equipment so as not to become part of the circuit. Step potential is also a concern when the ground is electrified. Shuffle feet to keep them as close together as possible.
Here is a table that shows the physiological effect to your body from exposure to increasing levels of electric current. It also details approximately how much voltage is needed to achieve these current levels based on assumed body resistance (Average ~10,000 ohms).
Physiological Effects Table
Electric Current (1 second contact)
Physiological Effect
Voltage
1 mA
Threshold of feeling, tingling sensation.
10 V
5 mA
Accepted as maximum harmless current. Intense involuntary spasms might lead to other injury.
50 V
4-5 mA
Current as which a typical GFCI will trip.
Designed to protect you
10-30 mA
Beginning of sustained muscular contraction (“can’t let go” current).
100 V
75-300 mA
Ventricular fibrillation, fatal if continued.
750 V
15000 mA
Lowest current at which a typical fuse or circuit breaker trips.
Designed to protect equipment
Electrical Safety Training
For a comprehensive overview of basic electrical safety and things to consider while working with and around electricity and electrical equipment, EHS has developed an online course for Electrical Safety Awareness. This course can be found in the ATLAS Learning Center Course Catalog.
NOTE: If you plan to design, build or modify electrically powered equipment for your research you will need more advanced knowledge and training than is currently offered through MIT EHS. Please contact environment@mit.edu if you have questions related to more in-depth electrical training needs or have plans to build or modify electrical equipment.
Understand your limitations when using electrical equipment
Identify the hazards associated with electricity: shock, fire and arc flash
Recognize unsafe electrical conditions and equipment
Familiarization with information listed on equipment tags: NRTL, energy needs, load capacities
Describe basic safety controls and practices when working with electrical equipment
Identify electrical emergencies and explain how to respond to them
National Consensus Standards for Design and Installation
To safeguard against injury when using electrical equipment, requirements and standards have been established through the implementation of nationally recognized codes, approval tests, and electrical safety work practices. This is to ensure that you have adequate training and experience when handling electrical equipment.
National Electrical Code (NEC)® – supported by the NFPA provides electrical safety requirements for wiring methods used in the workplace, for live electric supply and communication lines and equipment for employees in the workplace.
Basic Electrical Safety
Only licensed electricians are permitted to work on building infrastructural electrical systems.
Should a circuit breaker or other protective device “trip”, ensure that a licensed electrician checks the circuit and equipment and corrects problems before resetting the breaker.
Report hazards (lack of protective guards or covers, damaged equipment, etc.) to the building manager, Department of Facilities, Environment, Health, and Safety Office, or supervisor immediately.
Discard any piece of equipment that gives you even the slightest shock. If the resistance through your body is lowered i.e. standing in water or touching metal, even the slightest shock can be deadly.
Take seriously any warning signs, barricades, or guards posted when electrical equipment is being repaired, installed, etc.
Junction boxes and electrical panels need to have proper covers in place to conceal all wiring. Hard wiring should not be exposed/accessible to non-electrical employees.
Do not leave electrical boxes, switch-gear, cabinets, or electrical rooms open when not directly attended.
Remove materials, especially those that are combustible, such as paper and wood from the area in front of electrical panels. There should be 36” of clearance for safe access if needed.
Do not operate electrical tools or equipment in wet areas or areas where potentially flammable dusts, vapors, or liquids are present unless specifically approved for the location.
De-energize equipment before removing any protective covers or guards.
Do not use an electrical outlet or switch if the protective cover is ajar, cracked, or missing.
Never put conductive metal objects into energized equipment.
Remove the cord from the outlet by pulling the plug instead of pulling on the cord.
Do not carry equipment by the cord – only by the handle or base.
Extension cords are used to temporarily operate electric equipment in areas where there are no outlets. Relocatable Power Taps (RPTs), more commonly known as power strips add extra outlet space, while a surge protector also defends against possible voltage spikes that could damage your electronic equipment. The following best practices should be followed when using these devices.
Re-route electrical cords or extension cords so they don’t run across the aisle/corridor or over pipes or through doors.
Be sure extension cords are properly rated for the job and used only temporarily.
Use extension cords with 3-prong plugs to ensure the equipment is grounded. Never remove the grounding post from a 3-prong plug so you can put it into a 2-prong.
Do not overload extension cords, multi-outlet strips or wall outlets.
All surge protectors or power strips need to be UL (Underwriters Laboratory) or ETL (Electrical Testing Laboratories) approved. Unlisted items may not have been tested for safety
Do not plug a surge protector, power strip or an extension cord into an existing surge protector, power strip or extension cord. This practice is called “daisy chaining” or “piggy backing” and can lead to serious problems.
There should only be one surge protector or power strip plugged into a single duplex electrical outlet.
Do not locate a surge protector, power strip or extension cord in any area where the unit would be covered with carpet, furniture, or any other item that will limit or prevent air circulation.
Do not staple, tack, or tape a surge protector or power strip.
Do not plug any equipment using over 5 Amps or 600 Watts into a power strip. This equipment should be plugged directly into a wall outlet.
Limit surge protector or power strip load to 80% of capacity listed on back label.
GFCIs are designed to protect people from electric shock.
A GFCI works by detecting a current drop from the hot to the neutral wiring in a circuit. When the GFCI senses approximately a 5ma difference it shuts down the circuit in 1/40 of a second.
GFCIs must be installed wherever a water hazard is present.
GFCIs can be at the breaker, the outlet, incorporated with the plug of the appliance/piece of equipment, or part of a short extension cord.
Example Images of GFCIs:
Wiring, Grounding, Insulation
All electrical installations or the replacement, modification, repair, or rehabilitation of any electrical installation must comply with the requirements of the National Electrical Code (NEC) of the National Fire Protection Association, and/or the U.S. Department of Labors’ Occupational Safety and Health Administration.
All equipment should be grounded and fused in accordance with NEC. All extension cords must have a grounding pin.
All electrical equipment should be properly insulated. Any power cords that are frayed must be discarded and any live/hot wires should be insulated to prevent danger of electrical shock.
Documents
The following documents are Standard Operating Procedures (SOPs) related to electrical safety. MIT certificate login is required to view the SOPs and can also be located under Forms/SOPs (keyword search: electrical).
Hand-to-hand, hand- or head-to-foot, and ear-to-ear current paths are the most dangerous because it may cause severe damage to the heart, lungs, and brain. This is why it is important not to wear metal jewelry, not to lean against or use both hands-on electrical equipment so as not to become part of the circuit. Step potential is also a concern when the ground is electrified. Shuffle feet to keep them as close together as possible.
