Lockout / Tagout (LOTO) Reference
Why this matters
LOTO prevents the most-deadly workplace events: another worker turning power back on while you're inside. OSHA 1910.147 mandates LOTO for energy isolation. The tech who LOTOs every time goes home safe; the one who shortcuts gets injured OR killed. This is the field card.
OSHA Standard 1910.147 (Lockout / Tagout)
Required when:
- Service OR maintenance on machine OR equipment
- Energization OR release of stored energy could harm worker
- Bypassing of safety guards required
Energy sources covered: electrical, mechanical (gravity, springs, pneumatic), hydraulic, thermal, chemical.
Penalty for violation.
LOTO procedure (six steps)
- Notify affected workers: tell everyone the equipment will be down + LOTO'd
- Identify energy sources: all energy entering the equipment (electrical, gas, water, hydraulic, pneumatic, etc.)
- Shut down equipment: normal operating procedure to turn off
- Isolate energy sources: open disconnects, close valves, drain capacitors, bleed pressure
- Apply lock + tag: each worker applies own lock + tag to each isolation point
- Verify zero energy: test that equipment is truly de-energized before working
Lock types
Padlock (keyed): each worker has a unique key; multiple workers = multiple locks on same isolation point.
Combination lock: less preferred (anyone can open if combo shared).
Group lockout box / station: 1 lock per worker on the box; everyone's keys inside; equipment-side lock secures isolation.
Group lockout hasp (cluster): multiple worker locks on shared hasp at isolation point.
Spare lock: per OSHA, employer keeps spare key for emergency lock removal (with documented procedure).
Lockout devices
Breaker lockout: device that physically holds breaker in OFF position; padlock through hole.
Plug lockout: encases plug end; prevents reinsertion.
Valve lockout (gate, ball, butterfly): mechanical block on valve handle; padlock through.
Cable lockout: cable wraps around device; padlock secures.
Universal lockout devices (Master, Brady): cover variety of OEM equipment.
Tagout
Tag = paper / plastic identifier explaining who locked it + why + when.
Standalone tagout only when lockout not physically possible (rare). OSHA requires equivalent protection (e.g., removed control panel).
Tag content:
- "DANGER - DO NOT OPERATE"
- Worker name
- Date + time
- Reason (e.g., "Repairing compressor")
- Worker contact info
Color code: typically red OR yellow + black writing.
Energy verification
After LOTO, before opening: TEST FOR ZERO ENERGY.
Electrical:
- Multimeter on AC voltage at terminal: must read 0V
- Test multimeter on KNOWN live circuit first (proves meter works)
- Test target circuit (must read 0V)
- Re-test on known live (proves meter still works)
Hydraulic / pneumatic:
- Release stored pressure via bleed valve
- Visual confirmation gauge reads 0
Thermal:
- Allow heated equipment to cool
- Sensor / thermocouple verify temperature
Mechanical (gravity, spring):
- Lower OR block raised parts
- Discharge springs / energy storage
Capacitive + stored energy
Capacitors: hold charge after power off. HVAC capacitors + computer power supplies hold lethal charge.
Discharge before contact: insulated screwdriver across terminals OR dedicated discharge tool.
Wait time: typical 60 seconds for HVAC cap to discharge; verify with multimeter.
When LOTO is NOT required
Cord-and-plug equipment with single energy source + within sight of plug: unplugging suffices.
Adjustments + minor servicing during normal operation: if not exposing worker to energy hazard.
Hot work (work with energy intentionally present): only by authorized + qualified personnel; arc-flash PPE; not LOTO situation.
Common LOTO mistakes
Skipping LOTO for "5-minute job" (most accidents during quick fixes). Wrong isolation point (energy still flowing). Skipping verification step (assuming "locked = dead"). Removing someone else's lock (NEVER; OSHA violation; potentially fatal). Tagout-only when lockout possible (OSHA prefers lock+tag). Reusing lock with worn keying. Not training new techs.
Authorized + affected workers
Authorized: trained to apply + remove LOTO devices.
Affected: work in area; may operate the equipment normally; needs to know when LOTO is in place.
Other: anyone else in area; receives general training on LOTO awareness.
Group LOTO
When multiple workers on same equipment: each applies own lock to a group lockout hasp OR group lockout box.
Lead authorized worker: coordinates; assures everyone is clear before re-energization.
Each worker removes own lock when their portion done.
Final removal: lead authorized worker removes last lock + re-energizes after final verification.
Shift change LOTO
Outgoing worker does NOT remove lock at end of shift if work continues.
Incoming worker applies their own lock first, then outgoing removes theirs.
No "lock left for next shift" without continuity protocol.
Common service-tech LOTO scenarios
HVAC outdoor disconnect: pull fuses, lockout disconnect, lock with padlock, verify 0V at compressor + condenser fan.
HVAC indoor (air handler / furnace): shut off breaker at panel, lockout breaker, verify 0V at unit + transformer.
Plumbing electric water heater: shut off breaker, lockout, verify 0V at element terminals.
Garage door opener: unplug + lockout cord OR lockout breaker.
Pool pump: shut off breaker, lockout, verify 0V at motor.
Appliance repair: unplug (sight of plug = OK without padlock).
Documentation
Energy control procedures: written for each piece of equipment with multiple energy sources.
Periodic inspection: annual review per OSHA.
Worker training records: maintained for each authorized + affected worker.
LOTO logs (some jurisdictions): who LOTO'd what + when.
Truck stock
Padlock (keyed alike for one worker; 4 - 6 locks); breaker lockout (varies by brand); plug lockout cover; gas + water valve lockout; cable lockout; tagout tags + ties; permanent marker.
What to do if LOTO fails
Discovered live equipment after LOTO + verification step:
- Stop work immediately
- Re-energize at safe location
- Investigate failure (wrong disconnect? secondary energy source?)
- Retest LOTO procedure
- Re-train if procedure error
Worker exposed to live energy during work: medical eval; incident report; OSHA notification (if injury); review of LOTO procedure.
References
- OSHA 29 CFR 1910.147 (Lockout/Tagout Standard)
- OSHA 29 CFR 1910.333 (Electrical Safety-Related Work Practices)
- NFPA 70E (Standard for Electrical Safety in the Workplace)
- ANSI Z244.1 (Lockout/Tagout Personnel + Procedures)
- Manuall internal: PPE Selection by Task, Electrical Safety Reference