Different contaminants affect floor slip-resistance in different ways. Water is the standard test contaminant because it is the most foreseeable in UK pedestrian environments, but oil, soap, sugar, dust and biological contaminants each have their own slip-risk profile and may require modified testing approaches in forensic and research contexts.
Clean tap water at ambient temperature is the standard pendulum test contaminant for wet testing. Most UK pedestrian environments encounter water through rainfall, condensation, cleaning fluids, or food and drink spillage. The HSE PTV bands and most regulatory references are calibrated against water-wet performance.
Water performance is also a useful baseline for understanding how a surface would behave with other contaminants — typically, water is less aggressive than oil or soap on slip resistance, so water-wet PTV is roughly the upper bound of what other contaminants will produce.
Oil contamination produces lower PTV than water on almost every surface. Motor oil is the standard test contaminant for the BS EN 16165 Annex B shod ramp test (R-ratings) precisely because it represents a worst-case for kitchen and industrial environments.
For pendulum testing in oil-contaminated environments — kitchens, workshops, food processing — testing is sometimes carried out with oil rather than water, with the report explicitly stating the contaminant. Such testing is non-standard and the result cannot be compared directly to HSE PTV bands without context.
Soap and detergent contamination is dominant in changing rooms, public showers, hotel pools, and cleaning-cycle conditions in retail and hospitality. The slip-risk profile is between water and oil — soap reduces friction more than water alone but typically less than heavy oil contamination.
Annex A barefoot ramp testing uses a dilute soap solution as the standard test contaminant precisely because soap is the operational contaminant in barefoot wet environments. Pendulum testing in soap-contaminated zones is delivered wet (water) as standard, with soap-contaminated testing on request for specific forensic questions.
Sugar contamination is the dominant non-water contaminant in pubs, bars, cinemas, ice-cream parlours and confectionery production. Beer, soft drinks, syrup and confectionery residue produce a tacky, low-friction film that worsens as it dries before being cleaned.
Sugar-contaminated PTV is typically tested at the operational concentration of the spillage — for pub-floor work, a beer-strength sugar solution rather than pure water reflects the actual operating risk. Reports state the contaminant and concentration explicitly.
Dust contamination on a smooth dry floor can produce slip risk comparable to wet conditions. Flour dust on bakery floors, wood dust in joinery, and atmospheric dust in long-vacant retail premises all reduce dry PTV by interposing a layer between the slider and the surface. This is one of the few contexts where a 'dry' floor is not a 'safe' floor.
Biological algae growth on damp shaded paving is a significant external slip risk. Algae produces a gel-like film when wet that reduces PTV by 10–20 points compared with the same paving algae-free. Sweeping does not remove algae; biocide cleaning is the typical remediation.
For external paving testing, identifying whether algae is present, and whether the test result is from algae-affected or algae-free zones, is part of the report. Seasonal algae cycles mean that the same paving can produce very different PTV results across the year.
Frost and ice on external paving produce extremely low PTV — typically below 15. Pendulum testing of surfaces with surface frost is non-standard and the result is rarely useful: the instrument's slider does not behave normally on icy surfaces. Frost-risk assessment is better delivered through cold-weather inspection regimes than through pendulum testing of the frosted condition.
Real-world surfaces rarely have a single contaminant. A pub floor may have beer, food residue, water from cleaning, and customer-shoe-borne external mud. A supermarket entrance may have rainwater, store cleaning residue, and refrigerated condensation drift. Pendulum testing under standard wet (clean water) gives a baseline comparable across visits and against HSE bands; specific contamination testing can supplement this for forensic questions but cannot replace it.
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