Why do slip-and-fall accidents occur? Technically speaking, a slip occurs when the Coefficient of Friction or COF between the shoe material and the walking surface does not provide sufficient resistance to counteract the forward, resultant forces at the point of contact. This happens most commonly on wet floors or surfaces.
Why? Water, unlike air, does not easily compress, and when trapped between shoe and floor can form a continuous film leading to hydroplaning. Of course, hydroplaning is more common in environments where water is regularly present (i.e., entranceways during inclement weather, shower rooms, lobbies, and kitchens or food service areas).
According to the U. S. Department of Energy (DOE), a study of workers at DOE facilities who experienced injuries from slips and falls showed that approximately three-fourths of the indoor slip/fall events reported involved water.
Since a floor that is slip-resistant when wet will generally be slip resistant when dry, taking measurements of the condition of floors by benchmarking the wet COF - a number or range indicating how slip-resistant the floor surface is when it is wet or contaminated - is an important starting point to raise safety levels.
There are three steps to slip/fall prevention involving wet COF Measurement and data collection:
- Measuring and recording the condition of floors,
- Improving then maintaining that condition to a desired benchmark level through effective treatments and routine care, and
- Regularly evaluating / documenting the state of floors over time to help ensure (and demonstrate) the proper degree of due diligence, care, and compliance with safety norms.
According to Dave Ludwin, Director, General Liability Risk Control, CNA Insurance Companies: “It’s important to know what the starting slip resistance is on the floor materials in your facility. These numbers provide a baseline when considering changes to cleaning and floor maintenance practices. Then, going forward, have flooring COF audited periodically to determine slip resistance.”
The Binary Output Tribometer or BOT-3000 is a portable robotic device for both laboratory and on-site testing of dry and wet static and dynamic coefficient of friction. Since the BOT is an automated unit that can be calibrated in the field, user error or variability is minimized.
The BOT meets ASTM’s rigorous precision and bias requirements. It is also recommended by a major insurance carrier, and other expert groups.
Interestingly, early in 2006, Southlake, TX-based Regan Scientific Instruments, Inc. (fka Universal Walkway Testing, LP) - manufacturer of the BOT - submitted a BOT-3000 digital tribometer to Wuppertal University in Germany to study the correlation with the stationary German Ramp, Europe’s de facto standard for measuring slip-resistance.
According to Peter Ermish, principal of RSI: “The German Ramp Method (DIN 51130) is an established benchmarking test method in Europe and other countries for analyzing the slip resistance of footwear, floor surface materials, and coatings. Results to date show a close correlation between both devices/methods using a standardized test shoe material.”
Slip and fall prevention, and COF measurement science, have greatly progressed in recent years. Until recently, the goal was to achieve and maintain a .5 Static Coefficient of Friction (SCOF) on a dry floor surface. However, laboratory and field research have led to new, emerging and more practical benchmarks, since it is now clear that slips occur most often on wet floors in dynamic “in motion” environments.
ANSI B101.1 - “Test Method for Measuring Wet SCOF of Common Hard-Surface Floor Materials” – now in final development recommends a SCOF of .6 on wet floors.
The German Ramp Test (DIN 51130) sets an “in motion” Dynamic Coefficient of Friction (DCOF) target threshold of 0.45 or higher on a wet surface.
Thus, wet DCOF is becoming the new gold standard in slip/fall prevention measurement.
What to Do About Slippery Surfaces - Products and Treatments
If an existing wet floor's DCOF demonstrates that it is slippery, consider applying a specialized treatment or product to the surface that increases wet slip resistance.
Two product categories have proven effective in raising slip resistance on wet surfaces, and thus provide an excellent means to help ensure floor slip safety in general:
- Surface modifiers that raise traction levels of mineral containing floors (concrete, ceramic tile, stone, quarry tile, etc.)
- Mop-on cleaner/treatments that raise traction on finished and other floors.
Surface modifiers use chemical processes to alter the physical properties of an unfinished mineral-containing floor or surface improving the DCOF. The process creates micro-pores or imperceptible tread patterns rendering tile and stone floors safer to walk on when wet. Applying a penetrating sealer makes the surface more resistant to soil. Slip resistance lasts several years with proper regular cleaning. Application should be handled by professionals. Surface modifiers are also very effective on porcelain or ceramic tubs and showers.
Mop-on cleaner/treatments are high performance pH-neutral cleaners with ingredients that raise the slip resistance of finished and other floors. Though recommended dilution ratios must be followed, relatively unskilled employees can apply these water-based treatments for routine cleaning and maintenance of slip resistance.
Follow Up Testing and Documentation
The initial DCOF test should form the basis and reference point for all future recordkeeping and follow-up testing. This information should ideally be available both electronically and in hardcopy formats and should be readily available. The results of all future slips tests should be added to the existing file the day the tests are performed or shortly thereafter.
According to CNA’s Ludwin:
“A walkway auditing program can help identify trends within your facility that can result in reduced slip resistance to flooring surfaces. To be effective, the testing should be completed in a consistent, periodic manner and include more than a single set of measurements.”
Documentation should also include a guide and logbook outlining all standard cleaning procedures; the cleaning materials and equipment that are used; and enabling the recording of any slip/fall incidents - and the surrounding circumstances - that occur in the building.