What Makes a Floor Slippery?

A floor becomes slippery because of six factors working together, known as CHIMES: contamination, heel, individual, maintenance, environment and surface. No single factor decides slip risk on its own. It’s the combination that matters, and only one of these six, the floor’s surface, can actually be measured with a test.

The short why

Most people judge a floor’s safety by how it looks. A dry, clean looking floor feels safe, and a wet or dirty one feels risky. Slip resistance doesn’t work that way. It’s a physical property of the floor’s surface, combined with what’s on it, what’s being worn on it, and the conditions around it. Appearance only tells you about one of those things, and not the one that matters most.

The six factors behind every slip

We use the CHIMES framework to explain what actually drives slip risk on any floor, in any environment.

Each factor changes how risky a given floor is at any given moment. A floor with excellent surface grip can handle a reasonable amount of contamination safely. The same contamination on a floor with poor underlying grip can be genuinely dangerous, even if both floors look identical from a distance.

Why looks clean does not mean safe

This is worth stating plainly, because it’s where most assumptions go wrong. A floor can be mopped thoroughly, look spotless, and still carry poor slip resistance underneath. Grease can work its way into a floor’s texture over months of use without changing its appearance. Some cleaning products even leave a thin film behind that reduces grip while making the floor look shinier than before.

Slip resistance is measured using a pendulum test, which assesses how a standard test foot interacts with a floor surface under realistic wet conditions. This produces a Pendulum Test Value, or PTV, a number that tells you what a visual inspection cannot. Looking clean and testing safely are two different claims, and only one of them can actually be verified.

Why blaming a single factor rarely holds up

When a slip happens, it’s tempting to point to one obvious cause, the wrong shoes, a spill that wasn’t cleaned quickly enough, or poor lighting. In practice, most slips involve more than one CHIMES factor at once. A spill is far more likely to cause a fall on a floor with poor surface grip than on one with strong measured resistance, regardless of footwear or lighting. Treating any single factor as the whole explanation usually misses the bigger picture.

What to do about it

Start by testing the floor’s actual slip resistance with a pendulum test, since this is the one factor you can’t judge by eye. Once you know the surface score, look at the other five factors alongside it. Check what contamination the floor typically faces, what footwear is common in that area, how the floor is cleaned, and whether lighting or transitions make hazards harder to spot. Addressing the surface without considering the other five factors only tells half the story.

Take the next step

If you want to know how your own floors measure up across these six factors, the Slip Risk Scorecard is a quick way to find out where to start. For the full method behind assessing and improving slip risk properly, Slipology sets it out in detail.

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