3.5 Electrical Safety & Lockout/Tagout (LOTO)

Electrical Hazards and Terminology

Electricity represents one of the most lethal hazards in general industry and construction. Understanding fundamental electrical principles is essential for evaluating risks.

• Voltage (Volts, V): The measure of electrical potential or driving force pushing electrons through a conductor. Think of voltage as water pressure in a pipe.
• Current (Amperes or Amps, A): The flow rate of electrons through a conductor. Current is the primary variable that determines the severity of an electrical shock. Think of current as the volume of water flowing through the pipe.
• Resistance (Ohms, Ω): The opposition to the flow of current. The human body offers variable resistance; dry, intact skin provides high resistance (insulation), while wet or broken skin drastically lowers resistance, allowing more current to flow.

The Physiology of Electrical Shock

When a worker becomes part of an electrical circuit, the effects depend on the amount of current, the path it takes through the body, and the duration of the exposure.

• 1 mA: Barely perceptible tingling sensation.
• 5 mA: Slight shock; generally not painful but disturbing. Average "let-go" threshold for young children.
• 6-16 mA: Painful shock; loss of muscular control. The worker may be "frozen" to the circuit, unable to let go.
• 50-150 mA: Extreme pain, respiratory arrest, severe muscle contractions. Death is possible.
• 1,000-4,300 mA (1-4.3 Amps): Ventricular fibrillation (rhythmic pumping of the heart ceases). Nerve damage occurs. Death is highly likely.
• 10,000+ mA (10 Amps): Cardiac arrest, severe internal burns. Probable death.

Arc Flash and Arc Blast

Beyond shock, electricity presents thermal and kinetic hazards. An Arc Flash is a sudden release of heat and light energy caused by an electrical arc traveling through the air, often triggered by a short circuit or equipment failure. Temperatures can reach 35,000°F (four times hotter than the sun's surface), vaporizing copper and causing fatal burns. An Arc Blast is the explosive pressure wave created by the rapid expansion of air and vaporized metal during an arc flash. It can rupture eardrums, collapse lungs, and throw workers violently across a room.

To mitigate these risks, NFPA 70E establishes guidelines for electrical safety in the workplace, requiring electrical hazard analyses to determine Arc Flash Boundaries and specify appropriate Flame-Resistant (FR) PPE.

Protective Devices

Electrical systems utilize various devices to protect equipment and personnel.

• Fuses and Circuit Breakers: Overcurrent protection devices designed to protect equipment and wiring from overheating and fires due to short circuits or overloads. They generally trip at 15 to 20 Amps—far above the lethal threshold for humans. Therefore, standard breakers do not protect people from electrocution.
• Ground Fault Circuit Interrupters (GFCIs): Designed specifically to protect people. A GFCI monitors the current flowing out on the "hot" wire and returning on the "neutral" wire. If there is a discrepancy (as little as 4-6 milliamperes), it assumes the missing current is leaking to ground (potentially through a person) and shuts off the power in a fraction of a second.
• Grounding: Connecting electrical equipment to the earth through a conductive wire to provide a safe, low-resistance path for fault current, preventing the equipment casing from becoming energized.

Control of Hazardous Energy (Lockout/Tagout)

OSHA's standard for the Control of Hazardous Energy (29 CFR 1910.147), commonly known as Lockout/Tagout (LOTO), is critical for protecting workers who service and maintain machinery. The standard prevents the unexpected energization, start-up, or release of stored energy.

Types of Hazardous Energy

LOTO does not apply solely to electrical energy. A comprehensive program must address all forms of hazardous energy, including:

• Electrical
• Mechanical (moving parts)
• Hydraulic (fluid under pressure)
• Pneumatic (air under pressure)
• Chemical
• Thermal
• Potential/Gravity (suspended loads or compressed springs)

Employee Roles under LOTO

• Authorized Employee: A person who physically locks out or tags out machines to perform servicing. This is the only person allowed to apply and remove their specific lock.
• Affected Employee: An employee whose job requires them to operate a machine being serviced under LOTO, or whose job requires them to work in the area where servicing is being performed. Affected employees are not allowed to apply locks.
• Other Employees: Personnel who may pass through an area where LOTO is utilized. They must be instructed never to attempt to restart locked-out equipment.

The Six-Step LOTO Procedure

Before servicing begins, an Authorized Employee must follow specific steps:

1. Preparation for Shutdown: Identify the types and magnitude of energy, the hazards, and the methods to control the energy.
2. Machine Shutdown: Turn off the equipment using normal operating controls (e.g., stopping a motor via a control panel).
3. Energy Isolation: Physically locate and operate the energy isolating devices (e.g., throwing a disconnect switch, closing a physical valve). A standard push-button or emergency stop (E-stop) is a control circuit device, NOT an energy isolating device.
4. Application of LOTO Devices: Apply a physical padlock and warning tag to the energy isolating device to hold it in the "safe" or "off" position.
5. Control of Stored Energy: Relieve, disconnect, or restrain any residual or stored energy (e.g., bleeding air from a pneumatic line, inserting blocks under a hydraulic press).
6. Verification of Isolation: Attempt to restart the equipment using normal operating controls to confirm it will not turn on. Once verified, return controls to the "off" position before beginning work.