What is lockout/tagout (LOTO)?

LOTO is key to the field of environment, health and safety (EHS). It focuses on the protection of human health and the environment in various settings, such as worksites, communities and public spaces.

In most organizations, maintenance technicians perform LOTO as part of their normal maintenance activities before servicing equipment. LOTO activities are wide-ranging, encompassing both simple tasks like shutting off electrical circuits and more complex procedures like draining energy from hydraulic and pneumatic systems.

The term “lockout/tagout” refers to two complementary practices, fittingly called “lockout” and “tagout”:

• Lockout: The placement of physical locks—usually padlocks—on energy isolating devices like circuit breakers, valves and disconnected switches to ensure that they are de-energized.
• Tagout: The use of warning tags known as tagout devices to indicate that no one should operate a machine or piece of equipment until the tag has been removed.

Organizations rely on LOTO procedures wherever technicians must deal with hazardous energy as part of normal production operations like maintenance, cleaning and tool changes. If released or activated unexpectedly, a hazardous energy source is any form of energy that could cause injury or death to workers or damage the equipment. This aspect can include electrical, mechanical, hydraulic and pneumatic, thermal, chemical, gravitational or radiation.

According to a recent report, the global market for LOTO equipment was valued at USD 260 million. It is also projected to grow at a compound annual growth rate (CAGR) of 5–7% over the next 7 years.¹ OSHA estimates that LOTO procedures prevent 120 fatalities and 50,000 injuries annually in the United States alone.²

In the United States, the Occupational Safety and Health Administration (OSHA) regulates all LOTO programs through the Control of Hazardous Energy Standard (29 CFR 1910.147). This OSHA standard lays out all requirements for energy control programs, including safety training, lockout/tagout procedures and periodic inspection. While some OSHA regulations permit the use of tagout independently (without lockout), the OSHA framework prioritizes lockout because these procedures provide a physical barrier to device reactivation.

Lockout/tagout (LOTO) consists of seven energy control procedures that can be adjusted to fit the needs of specific assets or systems. Here’s a closer look at each step in the process.

Before initiating the shutdown, authorized employees identify the various hazardous energy sources contained in a piece of equipment. This step involves identifying both primary and secondary energy sources, including:

• Electrical equipment and circuit breakers
• Mechanical equipment with moving parts
• Hydraulic and pneumatic systems
• Thermal or chemical energy

During the preparation phase, engineers and technicians identify and familiarize themselves with the risks surrounding these different sources of energy so they can ensure complete energy isolation before repair start. 

When they’ve identified and isolated all affected sources of energy, workers bring the equipment to a safe state using operating controls like push buttons and control panels.

When performed correctly, a shutdown ensures workers won’t encounter an unexpected startup later in the process that might compromise their safety.

Phase three ensures all relevant energy isolating devices like disconnect switches, valves and blank flanges for piping systems are safely engaged. The goal of this step is to create a physical barrier separating equipment from all potential power sources.

The application phase involves authorized employees applying their own locks to isolation points to further ensure their own safety. In a multi-worker environment, LOTO regulations allow for the use of hasps and lockboxes to enable group lockouts. These safety tools include multiple locks that ensure a single isolation point for a piece of equipment and sources of energy.

During this phase, workers attach tagout devices to locks, clearly communicating that a piece of equipment must be powered down until the tag is removed.

The release phase, also known as the “release of stored energy” phase, is critical to ensuring no energy remains in a piece of equipment when workers are preparing to service it. Poorly draining residual energy from systems and equipment can result in injuries and fatalities in industrial settings.

In some organizations, the release phase is connected to larger process safety management (PSM) practices—systematic, enterprise-wide approaches designed to help employees handle hazardous chemicals safely.

Step five typically involves:

• Bleeding pressure from pneumatic or hydraulic lines to ensure no pressurized air or fluid remains in a system
• Discharging capacitors in electric equipment to remove residual energy
• Allowing heated components to cool so they don’t burn workers

In step six, an authorized employee performs rigorous inspections to ensure that a system has been fully de-energized and work on it can begin.

This step often includes repeated attempts to start a device or piece of equipment to ensure that no unexpected energization will occur during repairs.

When maintenance technicians conclude their work, the affected system or piece of equipment can be reenergized and restarted.

Authorized employees remove all locks and tags and verify that personnel are clear of the equipment, then restart the system and safely restore it to operation.

Lockout/tagout (LOTO) procedures help organizations realize measurable improvements in operational safety, compliance and other areas. Here’s a closer look at some of its most compelling benefits at the enterprise level.

• Reductions in workplace injuries and fatalities: Lockout/tagout programs help prevent worker injuries and fatalities due to unexpected startup or release of hazardous energy during repair. LOTO helps maintenance teams implement safety measures to eliminate risks at the source, wherever stored energy might have gotten trapped inside a system or device.

• Improved compliance: Proper LOTO procedures applied to a piece of equipment help organizations comply with the OSHA standards, CFR requirements and governance, risk and compliance (GRC) frameworks that govern their equipment and systems. LOTO procedures ensure that organizations aren’t penalized for non-compliance and help keep workers safe from hazardous materials.

• Increased standardization: Efficient energy control programs, a core function of a well-designed LOTO framework, help reduce the number of variabilities in how employees perform their tasks. With proper training, LOTO helps workers better understand their roles and responsibilities and rigorously follow safety procedures. For example, LOTO helps ensure that only authorized employees implement lockout/tagout on a specific piece of equipment and that affected employees have a clear understanding when LOTO is in place.

• Stronger operational discipline: LOTO helps reinforce existing operational practices, such as shutdown procedures, energy isolation and verification of machine operational status. LOTO reduces organizations’ reliance on informal, unsafe workarounds that cause unsafe working conditions. It replaces them with modern, compliant and well-established practices. 

• Longer asset lifecycles: While lockout/tagout is primarily a worker-safety practice, it also has value and benefits from an asset management perspective. LOTO helps preserve asset integrity and extend asset lifecycles by enforcing disciplined energy isolation and eliminating unexpected energization—both of which can damage assets and shorten lifecycles. Modern LOTO programs reduce mechanical stress, electrical faults and process-induced damage that degrade assets over time.

Lockout/tagout (LOTO) is applied across a diverse set of industries and workplaces—anywhere workers must deal with hazardous energy that could be trapped inside systems and equipment.

Here are some of its most common use cases.

Despite their overall effectiveness, modern lockout/tagout (LOTO) programs still face significant challenges. LOTO technicians frequently struggle with the complexity of modern systems and infrastructure that can lead to dangerous oversights and put workers directly at risk.

Here’s a closer look at some of the common problems that hamper LOTO:

• Infrastructure complexity: As a result of the rise of Industry 4.0, modern industrial systems feature more interconnected parts than ever. Artificial intelligence (AI) and the Internet of Things (IoT) have added meaningful capabilities and efficiencies to the workplace, but also complexity that makes fully shutting down hazardous energy sources a challenge.
• Human error: Even the most modern, technologically advanced LOTO procedures are vulnerable to human error. Skipping steps, improper handling of lockout/tagout devices and failure to strictly follow energy control procedures are a few examples of how human error can put an entire system at risk.
• Improper training: Improper training on LOTO procedures remains one of the biggest risk factors when trying to build a LOTO program. Enterprises often struggle to conduct strong lockout/tagout training at scale because it’s so resource-intensive. Leaders must be able to ensure that both authorized employees and affected employees fully understand the responsibilities and risks of an unexpected startup.
• Program maintenance: LOTO programs must be regularly updated and maintained to be effective. Like pieces of equipment, LOTO processes evolve over time and lockout/tagout procedures run the risk of becoming ineffective if they aren’t frequently reassessed. Outdated LOTO practices can lead to incorrect control methods that increase worker risk.
• Periodic inspection: The OSHA standard that governs LOTO practices requires periodic inspection and review of all procedures to obtain certification. Employers and organizations must inspect each energy control procedure annually, and OSHA inspectors must observe an authorized employee performing the required procedures to verify each step has been followed.