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Electrical Safety for Construction

Learning Objectives

  • Identify the basic principles of electricity.
  • Identify the primary hazards associated with electricity.
  • Identify control measures and safety-related work practices to minimize the risk associated with electrical hazards.
  • Identify the proper response procedures in the event of electric shock or fire.

Available in English

40 minutes

230 electrical related fatalities occur each year.

The National Institute for Occupational Safety and Health (NIOSH)

Electricity is everywhere, so reliable and useful these days that it is often taken for granted, and it is somewhat shocking how little is actually understood about its properties by the general public.

Electricity is something that you can’t see, hear, or smell, so it is critical to have a basic understanding of what it is and how it works in order to use it safely. 

It takes only a small flow of electric current through the human body to injure or kill. To work safely with electricity, a basic understanding of how it works is necessary. Current, voltage, and resistance are the basic terms used when talking about electricity. 

Current flow, measured in amperes, is the flow of electrons through a conductor such as copper wire. Metals and liquids are two excellent conductors of electricity. Current is the equivalent of the volume of electricity flowing through a wire. It is typically the amount of amperes that determines the severity of injury including the likelihood of death.

You can also be a conductor. This means electricity can flow through you just like water flows through a hose because your body is comprised mainly of water.

Voltage, measured in units called volts, is the amount of electrical force or pressure required to push current through a conductor. Another word for voltage is “potential.” Just as there is pressure in a water pipe even with no water flowing, there is voltage at a receptacle, even if current is not flowing.

Resistance, measured in units called Ohms, is a material that opposes electron flow or transmission. Much like water flowing from a hose, electricity flows through any available path, but more of it flows through the path of least resistance.

Insulating materials tend to resist the flow of electricity. Glass, rubber, plastic, ceramics, and dry wood are insulators. But, no insulating material is perfect.

Physical Properties of Electricity

  • Electricity cannot produce useful work or cause harm unless a current flows.
  • Electrical current will not flow until there is a complete circuit from negative to positive terminals.
  • Electricity always attempts to travel to the ground and will do so either directly or through another conductive material in contact with it.
  • Electricity, like water, always attempts to follow the path of least resistance.
  • Electricity travels at the speed of light and you will have no time to react to remove yourself from its path to ground before you become part of the circuit.

You will receive an electrical shock if:

  • You touch both wires of an electrical circuit at the same time;
  • You can touch the negative wire of an energized circuit and ground at the same time;
  • You can come in contact with ground and a conductive part that is in contact with a negative wire of an electrical circuit.

Grounding is the redirection of electrical flow through a pathway that safely dissipates the electrical current. Three-wire or three pronged cord sets are designed with a “hot”, neutral and ground wire. The purpose of the ground wire is to safely dissipate any stray electrical charge built-up within the tool it is attached to. Bonding is the connecting of two or more objects together using conductive wire for the purpose of equalizing electrical energy. When electrical energies are not equal, a current is established and can cause a shock. 

Check your work area for electrical hazards related to:

  • Equipment
  • Atmosphere
  • Poor housekeeping
  • Lighting
  • Moisture
  • Alerting techniques and barricades

Before plugging in any electrical appliance or tool, look for:

  • Loose connections
  • Frayed or missing insulation
  • Missing ground prongs on plugs
  • Damaged power tool housings
  • Ungrounded equipment
  • Damaged or worn wiring or cases

At the beginning of each day: 

  • Visually inspect tools, extension cords, GFCIs, and work areas prior to each use for damage or excessive wear.
  • Take a quick look at the service panel supplying power to your work area.

When an electrical hazard cannot be eliminated or guarded, employees must be protected against shock or electrocution through the use of personal protective equipment (PPE).

Examples of PPE

  • Protective footwear
  • Insulating rubber gloves
  • Protective face and eyewear
  • Rubber mats
  • Insulated tools

The OSHA lockout/ tagout standard is designed to prevent needless deaths and serious injuries to workers. Lockout/tagout is a method of keeping de-energized electrical equipment and power supplies from being re-energized once the power has been turned off. Before any maintenance is performed on equipment, all sources of electricity as well as process lines must be locked-out and tagged-out.  

Course Outline
  • Introduction
  • Basic Principles of Electricity
  • Primary Hazards Associated with Electricity
  • Protection Against Electrical Hazards
  • Response to Electrical Shock or Fire
  • OSHA 29 CFR 1910.330-335: Electrical Safety-Related Work Practices Standards
  • OSHA 29 CFR 1910.332: Training
  • OSHA 29 CFR 1926.400-449, Subpart K, Electrical
  • National Fire Protection Association Standards: NFPA 70, National Electric Code; and NFPA 70E, Electrical Safety Requirements of Employee Workplaces
  • National Safety Council Data Sheets American National Standards Institute (ANSI) C-2 Underwriters Laboratories National Electrical Code (NEC)