Prevent slips and falls with flooring friction measurement

Jan. 10, 2008
Measurement enables you to collect data and lay the basis for proper remedial and preventive actions, which in turn reduce injury, operational and other costs.

The axiom, “What is measured gets done,” applies well to preventing slips and falls if what you measure is the coefficient of friction (COF) of plant floors. Measurement enables you to collect data and lay the basis for proper remedial and preventive actions, which in turn reduce injury, operational and other costs.

Data collection and follow-up entails:

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  • Measuring and recording the condition of your floors
  • Improving, then maintaining, the floors to a desired benchmark level through effective treatments and proper care
  • Regularly auditing and documenting the state of floors to demonstrate the proper degree of due diligence, care and compliance with safety norms.

Measuring wet floors

Be wary of water. A study of workers at the U.S. Department of Energy (DOE) facilities who have experienced injuries involving slips and falls showed that about three-fourths of the indoor slip/fall events reported involved water, according to the DOE.

Before doing anything else, it’s important to benchmark the wet COF, a measurement that records the slip resistance of the surface when it’s wet or contaminated. This supports the rationale that if a floor is slip-resistant when wet, it’ll be slip-resistant when dry. You should quantify your results and standardize your recordkeeping by establishing a baseline COF, making improvements and taking follow-up measurements.

Several organizations, including the insurance carrier CNA and the National Floor Safety Institute (NFSI,, use or recommend a device called the Binary Output Tribometer, or BOT-3000 ( This is the only U.S. floor-testing device that has passed ASTM’s rigorous precision and bias standards, and can measure both the static and dynamic COF. The device is automated, eliminating user variables that can affect reading consistency. Digital printouts and uplinks enable sharing, saving and storing data, tracking trends and providing a legally sound numerical trail that documents improvements.

Coefficient of friction

Coefficient of friction (COF) is a number that indicates the degree to which a floor is slip-resistant. The COF is determined with an instrument that senses the slip resistance of a surface. Both static and the dynamic coefficient of friction measurements are useful in determining floor safety.

Static coefficient of friction (SCOF) is the ratio of the horizontal force needed to start an object sliding to the force pressing an object normal to the surface.

Dynamic coefficient of friction (DCOF) is the ratio of the horizontal force needed to keep an object sliding to the force pressing an object normal to the surface.

Raise traction

If a clean floor's COF demonstrates that it’s slippery when wet, consider applying a specialized treatment or product to the surface to increase wet slip resistance. Two product categories have proven effective for this purpose:

  • Surface modifiers that raise traction levels on concrete, ceramic tile, quarry tile, stone, marble and other similar floor surfaces
  • Mop-on cleaners/treatments that raise traction on finished and other floors.

Surface modifiers improve the coefficient of friction by chemically altering the mechanical properties of an unfinished mineral-based floor or surface. The process produces micropores or imperceptible tread patterns that render concrete, 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, but reapplication should be handled by professionals. Surface modifiers also are effective on shower floor areas.

Mop-on cleaners and treatments are high-performance, pH neutral solutions with ingredients that increase slip resistance. Though recommended dilution ratios are critical, relatively unskilled labor can apply these water-based treatments for routine cleaning and maintaining slip resistance.

Once the floor achieves a COF safety compliance benchmark of 0.5, 0.6 or greater, (see sidebar: “COF standards”) it will need regular, documented audits to help ensure the floor is being properly maintained and to initiate corrective adjustments as needed.

Implement policies and procedures

A written and enforced floor safety policy and procedures guide can help improve floor safety, while demonstrating management’s commitment to prevention. The policy and guide should address common causes of slips and falls, including poor worker training, lack of weather contingency planning, inconsistent hazard identification, inappropriate footwear and inadequate floor cleaning, among other factors. It should detail how to perform and document measurement, improvement and maintenance of floor surfaces.

New hires should be taught and tested on these policies and procedures, and current employees retrained and evaluated every six months to 12 months. Document, file and send instruction and follow up to appropriate persons within the organization.

Learn from incidents

If people have already slipped or fallen at your facility, examine the qualitative and quantitative loss data, where available, to help identify how, where and under what conditions the incidents occurred. Then, appropriately plan and direct your remedial efforts. Performing physical inspections of incident areas might offer insight about causes, enabling a more focused and effective loss-control process.

Qualitative analysis examines conditions, frequency, severity and other patterns. It determines what type of footwear was being worn. It investigates whether there was a contaminant on the floor. It asks if “wet floor” signs were in place. It checks to see if there was a floor mat in place. It asks whether this could have been a trip fall, instead of a slip fall. It documents the shift and time the event occurred.

Quantitative analysis, on the other hand, determines the value or amount of the losses, projects future losses based on past losses, and estimates the overall future cost of risk. This enables projecting a return on investment that compares the cost of loss-control measures against projected costs of business as usual. By implementing a scientific, measurable, audited and documented program that identifies and prevents the causes of slips and falls, you’ll reduce injuries, insurance premium dollars and direct costs. Moreover, you will be protecting your employees, customers and future profits.

COF standards

To paraphrase OSHA, “A reasonable measure of slip resistance is static coefficient of friction (COF). A COF of 0.5, which is based upon studies by the University of Michigan and reported in ‘Work Surface Friction: Definitions, Laboratory and Field Measurements, and a Comprehensive Bibliography,’ is recommended as a guide to achieve proper slip resistance. A COF of 0.5 isn’t intended to be an absolute standard value. A higher COF might be necessary for certain work tasks, such as carrying objects, pushing or pulling objects, or walking up or down ramps [or on wet surfaces].

Slip resistance can vary from surface to surface, or even on the same surface, depending upon surface conditions and employee footwear. Slip-resistant flooring material such as textured, serrated or punched surfaces and steel grating [or treatments] might offer additional slip resistance. These types of floor surfaces should be installed in work areas that are generally slippery from wet, oily or dirty operations. Slip-resistant type footwear might also be useful in reducing slipping hazards.”

The American National Standards Institutes’ (ANSI) A 1264.2-2001 “Standard for the Provision of Slip Resistance on Walking and Working Surfaces” recommends a static COF (SCOF) of 0.5 for walking surfaces under dry conditions. ANSI/NFSI B101.1 “Test Method for Measuring Wet SCOF of Common Hard-Surface Floor Materials” recommends a SCOF of 0.6 on wet floors.

Kenneth Fisher is an adviser to the National Floor Safety Institute (NFSI) and serves on the NFSI/ANSI B-101 committee, which is establishing a test method for measuring wet static coefficient of friction for common hard floor materials. He is chairman of a subcommittee (NFSI/ANSI B-101-2), which is developing a standard for chemicals and treatments for hard tile surfaces. He served on ASTM's F-15 committee dealing with slip/fall issues. Contact him at [email protected] and (859) 493-0701.

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