Putting the starter key in your pocket during maintenance or repair work prevents anyone else from accidentally starting the machine while you’re working on it. This simple habit is one of the most effective ways to protect yourself from a category of workplace injury that kills over 200 people a year in the United States alone. In 2024, 213 workers died from being struck, caught, or compressed by running powered equipment, according to the Bureau of Labor Statistics.
The logic is straightforward: if the key is in your pocket, nobody can turn the machine on. Not a coworker who doesn’t realize you’re underneath it, not someone who assumes the job is finished, and not a gust of vibration that nudges a switch. You hold the only object that can bring the engine back to life, and you decide when that happens.
How It Fits Into Lockout/Tagout Safety
The “key in pocket” practice is part of a broader safety system called lockout/tagout, or LOTO. The idea behind LOTO is that before anyone services, cleans, or repairs a piece of equipment, all energy sources powering that machine need to be fully shut down, locked in the off position, and physically verified as dead. Energy doesn’t just mean electricity. It includes hydraulic pressure, compressed air, springs under tension, and raised components that could fall under gravity.
The standard sequence looks like this: shut the machine down using normal controls, disconnect or isolate every energy source, release any stored energy (like bleeding hydraulic lines), then lock and tag the isolation points so no one can reverse the process. After locking everything out, you verify the machine is truly off by trying to start it. Only then do you begin work. The key to any lock you placed stays on your person the entire time.
OSHA’s hazardous energy control standard spells out a principle that applies directly here: an energy control device must remain under the exclusive control of the worker performing the service. For plug-in equipment, that means the plug has to be in your hand, within arm’s reach, or locked out. For keyed machines, the equivalent is the ignition key sitting in your pocket. The moment someone else can access that key, you’ve lost exclusive control, and the protection breaks down.
Why Turning It Off Isn’t Enough
Switching a machine to “off” without removing the key leaves you exposed. Push buttons, selector switches, and emergency shutoffs are control-circuit devices, not true energy isolation points. They can be bumped, overridden, or simply flipped by someone who walks up and assumes the machine should be running. Safety guidelines explicitly state that these controls cannot substitute for proper lockout.
Removing the key and keeping it on you eliminates ambiguity. There’s no scenario where a well-meaning coworker “just checks if it starts.” There’s no scenario where an automated system cycles back on. The machine physically cannot restart because the ignition circuit is broken, and only you can close it again.
Group Work and Key Management
When multiple people are working on the same machine, key control becomes more structured but follows the same principle. In group isolation procedures, the isolation coordinator places all lock keys into a locked box. Each worker then attaches their own personal padlock (with their name on it) to that box. The machine cannot be restarted until every single worker removes their personal lock, confirming they’re clear of the equipment. Only then can the coordinator open the box, retrieve the keys, and unlock the isolation points.
This layered system ensures that no individual worker can be overruled. Even a supervisor can’t restart the machine while someone’s personal lock is still on the box. Every person working on the equipment has veto power over re-energization, and that power lives in the lock they physically control.
Preventing Theft and Unauthorized Use
The pocket habit has a secondary benefit that extends beyond maintenance safety. Heavy equipment is notoriously easy to steal because many machines across a manufacturer’s lineup use identical ignition keys. A single key can start dozens of different models from the same brand.
This vulnerability is serious enough that insurance companies often refuse to cover construction equipment unless owners install aftermarket anti-theft systems like secondary locks, tracking devices, or immobilizers. Lending institutions that finance equipment purchases frequently demand the same proof before approving a loan. Keeping the key on your person when you step away from a machine, even briefly, is the simplest line of defense against someone unauthorized climbing into the cab and driving off.
Beyond theft, there’s the risk of untrained personnel operating equipment they have no business touching. An unlocked, keyed machine is an invitation to anyone curious or reckless enough to try it. A missing key stops that scenario before it starts.
Modern Push-Button Start Systems
Newer equipment increasingly uses proximity fobs or push-button ignition instead of traditional keys. This changes the physical action but not the underlying rule. If your machine uses a fob, you keep the fob in your pocket during maintenance. The principle of exclusive possession remains the same.
Some industrial settings use purpose-built “key in pocket” interlock systems. These go further than a standard ignition key. The system physically prevents safety interlocks from being reset unless the operator’s personal key is inserted. When you pull the key and pocket it, the machine cannot cycle back to its operational state regardless of what buttons someone presses. These systems are common on automated production lines where a worker might need to enter a guarded zone for adjustments or repairs.
Mining and Construction Regulations
Federal mining safety regulations under MSHA require that repairs or maintenance on machinery be performed only after the power is off and the equipment is blocked against hazardous motion. While the regulation doesn’t use the phrase “key in pocket,” the practical implementation on any keyed machine means removing and retaining the key as part of de-energization.
Australian workplace safety guidelines from SafeWork NSW go further in specifying the key handling procedure: “The key to the isolation lock should remain with the Isolating Person and this can also be the same person undertaking the work on the machine.” The worker doing the job holds the key. Full stop. This isn’t optional guidance in those jurisdictions. It’s the expected standard of practice, and deviating from it during an incident investigation would be difficult to defend.
Making It a Habit
The hardest part of this practice is consistency. When you’re doing a quick fix that should take two minutes, pocketing the key feels unnecessary. But unexpected startups don’t happen on a schedule, and the consequences of one are catastrophic: crushing injuries, amputations, and fatalities. The workers who appear in those annual fatality statistics weren’t doing anything unusual. They were performing routine work on machines they operated every day.
Build the sequence into muscle memory: turn off the machine, remove the key, put it in your pocket, verify the machine won’t start, then begin work. When you’re done, visually confirm everyone is clear, reinsert the key, and restart. The few seconds this adds to every job are the cheapest safety investment you’ll ever make.