What STKY means on site

Every site has a list of things that can kill a person. Most crews can recite part of it. Almost none can recite all of it for the task in front of them, and the gaps are where serious injuries come from.

STKY is the name for that list: Stuff That Kills You. The name came from the field, and Dr Matthew Hallowell, whose research the programme is built on, uses it in his book. It is blunt on purpose, because the point of the name is that nobody forgets it.

Why a separate list

For decades, minor injury rates fell across most industries. Serious injury and fatality rates did not fall at the same pace. The explanation that drove Energy-Based Safety is that the two kinds of event have different causes. Minor injuries come from low-energy events that ordinary controls handle well. Fatalities come from high-energy releases, where only a specific class of control works.

That means a safety programme that treats every hazard the same way will spend most of its effort on the events that were never going to kill anyone. STKY is the correction. It separates the hazards that can kill from the ones that housekeeping, procedure and attention can manage.

The threshold

The line between the two is energy. Hallowell’s research puts the high-energy threshold at roughly 1,500 joules. Above that, the most likely outcome of contact is a serious injury or death.

Numbers are hard to picture, so the programme translates them into situations.

1. A person working at height above about 1.2 metres
2. A suspended load
3. A vehicle or mobile plant moving near people on foot
4. Exposure above 50 volts
5. An unsupported trench deeper than 1.5 metres
6. Steam, or anything that could explode

Hallowell’s book describes a set of common high-energy icons like these, and is clear that they are examples, not the full list. Some hazards need a calculation. A falling tool can cross the threshold depending on its mass and the drop.

The CHASNZ guide for New Zealand construction adds a second trigger: a health hazard that exceeds a workplace exposure limit counts as STKY too, because it can cause serious or fatal ill health, even when the harm is slow.

The Energy Wheel is how you find it

Knowing the threshold does not help if you cannot see the energy. People miss hazards they have no category for, and experience does not fix it: Hallowell’s team found experienced workers were just as likely to miss hazards as new ones.

The Energy Wheel lists ten sources: gravity, motion, mechanical, electrical, pressure, temperature, chemical, biological, radiation and sound. Walking a task against the wheel is a deliberate scan. For each source, is it present? If it is, how much? Is it above the line?

Done honestly, this takes a few minutes and finds hazards that an instinctive look skips. In workshops we run it twice on the same scene, first by instinct and then with the wheel, and the second pass usually finds more. That gap is the lesson.

What to ask of a STKY hazard

A STKY hazard is a high-energy hazard: one that can kill. The first question for each one is whether it has a Direct Control. That is the aim, and the test is strict.

A Direct Control is a real energy control: timely, tangible and targeted at the specific high-energy source. It works when installed, verified and used properly. And it stays effective even if a person makes an unintentional mistake during the work.

Sometimes no Direct Control is possible yet. Then the work needs Alternative Controls: at least two independent measures that reduce the chance of an error, such as a physical obstacle, dedicated monitoring or a visual reminder. They do not count as a Direct Control, so in a control assessment the hazard still scores as an exposure.

Training, procedures, signage and general PPE support safety, but they are not energy controls at all. A hazard that can kill should never be marked as controlled because of them.

On site, in practice

A crew that has absorbed STKY behaves differently in small ways. Pre-starts spend less time on the trip hazard by the container and more on the excavator swing radius. Someone asks “what is the Direct Control on that” and expects an answer that points at something physical. When the answer is “we will be careful”, the work pauses.

Supervisors get a shared word with the people doing the work. “That one is STKY” ends an argument about whether a hazard deserves attention. The argument that follows, about whether the control is really Direct, is the one worth having.

None of this needs new paperwork. It needs the crew to be able to name the energy, place it against the threshold and test the control. That is the whole skill, and it is teachable.

If you want to see how the Energy Wheel and the threshold are taught, see the VR workshops.