A complex lockout tagout is one that no single person controls from start to finish: the work outlasts a shift, several crews or contractors work under the same isolation, or the locks stay on for days. Every handover is a point where protection can lapse. In Switzerland, more than ten people die each year during maintenance on machines and plant.[1]
Your procedure has to answer four questions before the job starts:
- Who coordinates the lockout and holds the keys to the isolation locks?
- How does protection pass from one shift to the next without a gap?
- What changes when the work runs for days or a contractor joins?
- Who may remove a lock whose owner has gone home?
Part 1: What Is a Complex Lockout Tagout?
A basic lockout is one worker, one machine, one padlock, following the steps of lockout tagout. A complex lockout tagout adds people, time or companies, and with them handovers. Most use a group lockbox: the coordinator locks the isolation points and puts those keys in the box, then each worker adds a personal padlock. Our guide to group lockout explains the method. This post covers the harder cases.
| Situation | Where protection fails | Control |
|---|---|---|
| Shift change | Off-going locks come off before oncoming locks go on | Oncoming worker locks on first |
| Multi-day lockout | Nobody owns the isolation overnight | Coordinator's lock stays on; tags kept current |
| Several crews or contractors | One crew assumes another isolated a source | One named coordinator; a padlock for every person |
| Owner absent | Lock removed without checking the machine | Written removal rule; spare key out of reach |
All four use the same hardware: group lockboxes with room for one padlock per person.
Part 2: Lockout Tagout at Shift Change: Lock Transfer Without a Gap
HSE reports that many accidents have followed failed communication at shift handover, most during planned maintenance; the Cullen inquiry named it as one factor in the Piper Alpha disaster.[2] The lockout rule: the oncoming crew locks on before the off-going crew locks off.
The handover, step by step
- Meet at the machine. Hand over face to face, spoken and written: what is isolated, what is done, what is still open.[2]
- The oncoming worker checks the isolation points and tags against the procedure, then puts a personal padlock on the group lockbox.
- Only then does the off-going worker remove theirs.
- Both sign the handover log, with names and time.
The LOTO Dustproof Padlock - Steel - 38mm is keyed different, and its key cannot be withdrawn while the shackle is open, so no one walks off with the key of an open lock.
Best Practice: Give the coordinator a lock that stays on the group lockbox for the whole job, across every shift. If one crew leaves before the next arrives, the isolation still holds. That lock comes off last, once everyone is confirmed clear.
Part 3: Long-Duration and Multi-Day Lockouts
HSE advises planning maintenance so it is finished within one shift where possible.[2] When it cannot, the isolation has to survive nights, weekends and absences:
- Someone owns it at all times. The coordinator's lock stays on; the procedure names a deputy.
- Tags stay current. Each tag gives the name, how to reach that person, the purpose and the expected duration.[1][3]
- Keys stay visible. A lockbox with a window, mounted at the machine, shows each shift that the keys are inside.
- Re-check on return. At the start of each shift, read the gauges and bleed points again: a valve can pass and pressure can build up.
Part 4: Several Crews and Contractors on One Lockout
When electricians, fitters and a contractor work on the same line, each crew tends to assume another has isolated a source. Name one coordinator for the whole job: DGUV asks for a single responsible person,[3] and Suva for one person who coordinates in-house maintenance, contractors and production.[4]
Every person still applies their own padlock; DGUV rules out group locks whose keys all fit.[3] A main switch usually takes up to three locks, so larger crews need a hasp.[3] The Sliding Safety Hasp - Aluminium takes 12 or 24 padlocks at one point. Give contractors padlocks in their own colour, and brief them on site rules first.[4]
Real-World Case: Several people serviced a conveyor and secured it with a single lock. When the work was done, the lock came off and the plant restarted without anyone checking that it was empty. One person was drawn in and injured.[3] One lock per person and a final check prevent this.
Part 5: Removing a Lock When the Owner Is Absent
Each person removes their own lock and keeps the key on them.[1][3] For the day someone goes home with their lock still on, write the removal rule in advance:
- Confirm that the owner has left the site, and try to reach them.
- The coordinator checks the machine and the danger zone: work stopped, tools out, nobody inside.
- A named manager removes the lock with the spare key. DGUV allows a spare key only where other staff cannot reach it, for example with the production manager or foreman.[3]
- Record the removal, and tell the owner before they start work again.
Part 6: What EU, German, Swiss and French Rules Require
- EN ISO 14118: the machine side: isolating devices, locking devices and means to dissipate stored energy (clause 5).[5]
- Germany: DGUV Information 209-015: one responsible person (2.4.1); a padlock per person, spare key out of reach (3.1.1).[3]
- Switzerland: Suva's eight life-saving rules for maintenance, rule 3: personal padlock, key kept on you, tag.[1]
- France: INRS ED 6109, section 4.2: the procedure coordinates lockout and its removal at shift changes and over several days.[6]
- US, for comparison: OSHA 1910.147(f)(3) group lockout, (f)(4) orderly transfer at shift change, (e)(3) removal when the owner is absent.[7]
To write them into your procedure, see our lockout tagout procedure guide.
Part 7: Where The Lock Box Fits
Our group lockboxes for complex lockout tagout take one padlock per worker.
For a lockout that stays on for days, the Wall Mounted Group Lock Box - Large mounts at the machine, has room for 15 locks, a key slot on top and a clear window, so each shift can see the isolation keys. Add the sliding hasp for large crews, and keyed-different padlocks in one colour per crew or contractor. Write the lockbox, the coordinator and the shift handover into each machine's procedure with our free lockout/tagout procedure template (PDF, Word or Excel).
Planning a Lockout That Runs Across Shifts?
Contact The Lock Box with the number of isolation points and people per shift, and we will suggest a lockbox, hasp and padlock set. For digital handover records, see our sister brand Zentri.
References
- Suva. Acht lebenswichtige Regeln für die Instandhaltung von Maschinen und Anlagen: Instruktionshilfe (88813.d), rule 3 (2022). https://www.
suva. ch/ 88813. d - HSE. Shift handover (human factors topic). https://www.
hse. gov. uk/ humanfactors/ topics/ shift- handover. htm - DGUV. DGUV Information 209-015: Instandhaltung an Maschinen und Anlagen, sections 2.4.1 and 3.1.1 (June 2026). https://publikationen.
dguv. de/ regelwerk/ dguv- informationen/ 338/ instandhaltung- an- maschinen- und- anlagen - Suva. Checkliste: Instandhaltung von Maschinen und Anlagen (67192.d), items 6 and 7 (2023). https://www.
suva. ch/ 67192. d - ISO. ISO 14118:2017: Safety of machinery, Prevention of unexpected start-up, clause 5. https://www.
iso. org/ standard/ 66460. html - INRS. ED 6109: Consignations et déconsignations, section 4.2 (3rd edition, October 2020). https://www.
inrs. fr/ dam/ inrs/ CataloguePapier/ ED/ TI- ED- 6109. pdf - OSHA. 29 CFR 1910.147: The control of hazardous energy (lockout/tagout), paragraphs (e)(3), (f)(3) and (f)(4). https://www.
osha. gov/ laws- regs/ regulations/ standardnumber/ 1910/ 1910. 147