Lockout/tagout (LOTO) is the OSHA-mandated procedure for isolating hazardous energy before anyone opens, repairs, or reaches into a piece of equipment. In a research lab it applies to exactly the equipment that already sits at the center of daily bench work: autoclaves, centrifuges, chillers, vacuum pumps, lasers, and cryogenic freezers all store or deliver energy that can injure someone doing “just a quick fix” while the machine is still live. This guide covers the regulatory basis, the six-step procedure, the specific stored-energy hazards of common lab equipment, and where a lab’s lockout/tagout responsibility ends and facilities’ begins.
The regulatory basis: OSHA 29 CFR 1910.147
Lockout/tagout is governed by OSHA 29 CFR 1910.147, “The Control of Hazardous Energy (Lockout/Tagout).” The standard applies to the servicing and maintenance of machines and equipment where the unexpected energization, start-up, or release of stored energy could injure an employee. It requires employers to establish a written energy control program, train authorized and affected employees, and use lockout devices as the primary method of control (tagout alone is permitted only where the equipment is not capable of being locked out).
Federal OSHA’s general industry standard does not carve out an exception for laboratories as a class of workplace — a lab autoclave or centrifuge undergoing service is treated the same as an industrial machine undergoing service. Institutions in OSHA state-plan states (California, Washington, Michigan, and others) should check for state-specific LOTO requirements, which can be more stringent than the federal standard.
The cord-and-plug exception
Not every piece of bench equipment requires a full lockout procedure. Under 1910.147(a)(2)(ii), cord-and-plug-connected equipment is exempt from lockout/tagout if all three conditions hold: unplugging the equipment fully de-energizes it, the plug is the only energy source, and the employee doing the servicing has exclusive, physical control of that plug for the entire task (it stays within reach or in their pocket — not just “unplugged and left on the bench”). A benchtop centrifuge serviced by unplugging it and keeping the cord in hand typically qualifies for this exception. A centrifuge with a secondary energy source — for example a vacuum line, a refrigerant circuit, or residual rotor momentum that isn’t fully arrested by unplugging — does not.
Authorized vs. affected persons
The standard defines two roles, and confusing them is one of the most common lab-level compliance gaps:
- Authorized employee — the person who actually performs the lockout/tagout and does the servicing or maintenance. In a lab this is typically the person doing the repair: a trained lab manager, an institutional facilities technician, or a vendor field engineer, not necessarily the PI or the grad student who normally runs the equipment.
- Affected employee — anyone whose job requires them to operate the equipment, or to work in the area while it’s being serviced, but who does not perform the lockout themselves. Every other lab member who uses the autoclave, centrifuge, or laser is an affected employee for that service event and must be notified before and after the lockout.
An employee can be authorized for some equipment and merely affected for other equipment in the same room — authorization is task-and-equipment specific, not a blanket lab role, and it requires documented training on the specific energy control procedure for that machine.
The six-step lockout/tagout procedure
OSHA’s own “typical minimal lockout procedure” (1910.147 Appendix A) maps onto six practical steps. This is the sequence a lab’s written energy control procedure should follow for each piece of equipment:
- Prepare for shutdown. The authorized employee identifies which energy sources the equipment has (electrical, thermal, pneumatic, hydraulic, mechanical/stored, cryogenic) and reviews the equipment-specific procedure before touching anything.
- Notify affected employees. Everyone who uses the equipment or works near it is told that it will be shut down and locked out, and roughly how long it will be unavailable.
- Shut down the equipment using its normal operating controls — not by pulling a breaker or yanking a plug while it’s mid-cycle.
- Isolate the energy source(s). Open the disconnect switch, close the valve, remove the plug, or otherwise physically separate the equipment from every energy source identified in step 1.
- Apply lockout/tagout devices. The authorized employee attaches their own lock (or tag, only where the device cannot physically be locked) to each isolation point, and applies a warning tag identifying who applied it, the date, and why.
- Relieve, restrain, or verify the dissipation of stored (residual) energy — bleed residual pressure, block a raised component, discharge a capacitor — and then verify a true zero-energy state before beginning work, for example by attempting the normal start control (with the authorized employee clear of the hazard) and confirming nothing happens.
At the end of the job, re-energization follows the reverse sequence: confirm the area is clear, remove tools, reinstall guards, notify affected employees, and only then does the authorized employee who applied the lock remove their own lock and restore power.
Stored energy in common lab equipment
Isolating the plug is rarely the whole job. Most lab equipment has at least one secondary energy source that keeps presenting a hazard after the main power is cut, and that secondary source is exactly what a generic “unplug it” habit misses.
| Equipment | Primary energy | Stored / residual energy | Isolation point |
|---|---|---|---|
| Autoclave | Electrical (heating element) and building steam supply | Residual chamber pressure and superheated steam/condensate | Main electrical disconnect plus the steam or water supply valve; chamber must be depressurized and cooled before the door is opened for service |
| Centrifuge | Electrical (motor) | Rotor momentum after power-off; some models retain a vacuum in the chamber | Plug or disconnect, and the rotor must be allowed to come to a complete stop (never braked by hand) before the chamber is opened for service |
| Chiller / recirculating cooler | Electrical (compressor, pump) | Pressurized refrigerant circuit; hot compressor surfaces | Electrical disconnect; refrigerant work requires EPA-certified technicians and is normally a facilities/vendor responsibility, not a bench task |
| Vacuum pump | Electrical (motor) | Residual vacuum in connected lines and traps; oil-mist discharge | Plug or disconnect, plus bleeding the vacuum line to atmosphere before disconnecting fittings |
| Class 3B/4 laser system | Electrical (power supply) | High-voltage capacitors that remain charged after shutdown | Main disconnect and manufacturer-specified capacitor discharge procedure; only the Laser Safety Officer or a qualified authorized person should open the housing |
| Cryogenic freezer / LN2 dewar system | Electrical (compressor, controls) | Residual cryogen, oxygen-displacement hazard in an enclosed room, cold-burn risk from surfaces | Electrical disconnect and isolation of the cryogen supply line; area ventilation/oxygen monitoring should be confirmed before service in enclosed spaces |
This is why the written procedure for each machine has to be equipment-specific rather than a single lab-wide LOTO memo: the isolation points and the stored-energy check are different for a steam autoclave than for a laser power supply, even though both start with “unplug it.”
Lockout devices and tags
OSHA requires that lockout devices be standardized within a facility by color, shape, or size, and that tags be legible and durable enough to withstand the environment (an autoclave room’s heat and humidity has degraded paper tags in practice). Common lab-relevant devices:
- Plug lockout — a lockable enclosure around a male plug, used when the cord-and-plug exception doesn’t apply (shared equipment, multiple potential operators, or a secondary energy source).
- Breaker lockout — a clip or clamshell device that physically prevents a circuit breaker from being switched on.
- Valve lockout — for gas, steam, or water supply lines feeding autoclaves and some chillers; ball-valve and gate-valve lockouts are the two common styles.
- Group lockout box / hasp — used when more than one authorized employee is working on the same piece of equipment (see below); each person’s individual lock goes on the hasp or box rather than directly on the isolation point.
Every tag, regardless of device type, should identify who applied the lockout, the date, and the reason — “do not operate” alone, without attribution, does not meet the intent of the standard and leaves the next person unable to tell whether it’s safe to ask around before removing it.
Group lockout in shared and core facilities
Shared instrumentation rooms and core facilities are where lab lockout/tagout most often breaks down, because more than one authorized person — a facilities electrician and a vendor field engineer, for example — may need to work on the same piece of equipment across a single service event. OSHA requires that group lockout provide each authorized employee the same level of protection as an individual lock would: each person attaches their own personal lock to a group lockbox or hasp when they begin work and removes it when they stop, so the equipment cannot be re-energized until every individual who is still working on it has cleared out. During shift changes or when one authorized employee’s task ends while another’s continues, the facility’s procedure needs an explicit transfer step so the machine is never briefly unlocked between two authorized people’s shifts.
Where the lab’s responsibility hands off to facilities
Most labs are not responsible for isolating a building’s central utilities — they’re responsible for the equipment itself and, in many institutions, for cord-and-plug-exempt bench work only. A practical line to draw:
- Lab-level (often the PI, lab manager, or trained lab staff): cord-and-plug servicing that meets the exception above — for example, replacing a fuse or filter on a benchtop centrifuge after confirming it’s unplugged and the plug stays in the servicing employee’s control.
- Facilities/EHS-level: anything touching a building utility — steam risers feeding an autoclave, central vacuum or chilled-water systems, building electrical panels, refrigerant work on a chiller — is normally isolated and locked out by facilities or a certified vendor, coordinated through the institution’s EHS office and its own written energy control procedures for those systems.
The handoff should be explicit in the lab’s own written procedure: if a repair requires opening anything beyond the equipment’s own accessible panel, the default should be to stop and call facilities/EHS rather than a lab member isolating a building-level source they were never trained or authorized on.
Training and periodic review
OSHA requires initial training for both authorized and affected employees — authorized employees need to understand the specific hazardous energy sources of the equipment they service and the methods to control them; affected employees need to understand the purpose of the procedure and recognize when it’s in use, without needing to perform it themselves. 1910.147(c)(6) also requires the employer to conduct a periodic inspection of each energy control procedure at least annually, to confirm the steps are still being followed correctly and to identify any deviations or corrections needed — a requirement that’s easy for a lab to lose track of once the initial procedure is written, since it’s an ongoing certification rather than a one-time document.
Frequently asked questions
Does lockout/tagout apply to all lab equipment?
Only equipment that isn’t fully covered by the cord-and-plug exception. If unplugging the machine completely removes all hazardous energy and the person doing the work keeps the plug under their own control the whole time, formal lockout/tagout isn’t required for that task. Equipment with a secondary energy source — steam, vacuum, refrigerant, stored mechanical energy, or a charged capacitor — needs a full lockout procedure regardless of whether it’s also plugged into a wall outlet.
Can a grad student or lab tech be an authorized employee?
Yes, as long as they’ve received the specific training the standard requires for that equipment’s energy control procedure — there’s no seniority requirement in the standard itself. What matters is documented training on the actual hazards and isolation methods, not job title.
What’s the difference between lockout and tagout?
Lockout uses a physical device (a padlock) that prevents the energy-isolating device from being operated. Tagout uses a warning tag instead, without necessarily preventing operation. OSHA requires lockout as the primary method wherever the equipment is capable of being locked out; tagout alone is only acceptable where the isolating device has no provision for a lock, and even then the standard requires additional safety measures to provide equivalent protection.
Who removes the lock when service is finished?
Normally, only the authorized employee who applied the lock removes it. If that person is unavailable and the lock must be removed by someone else, OSHA requires a specific procedure — verifying the original employee is genuinely gone, making a documented attempt to contact them, and ensuring they’re informed the lock was removed before they resume work.
Does a fume hood or biosafety cabinet need lockout/tagout?
Servicing a fume hood’s or biosafety cabinet’s fan, ductwork, or electrical controls follows the same energy-control logic as any other lab equipment — the airflow system needs to be de-energized and verified before internal service. See CASRAI’s guide to autoclave operating safety and comparison of biosafety cabinets, fume hoods, and laminar flow hoods for the airflow-verification side of that work.
Related CASRAI guides
- Autoclave Operating Safety: Avoiding Steam Burns and Pressure-Related Injuries
- How to Operate a Lab Autoclave: Cycle Types Explained
- Autoclave Troubleshooting: Common Problems and Fixes
- Centrifuge Rotor Balancing: Safety Best Practices
- Laser Safety Classes Explained: From Class 1 to Class 4
- Biosafety Cabinet vs. Fume Hood vs. Laminar Flow Hood
