What is cross-contamination in cleaning?

Cross-contamination occurs when bacteria, viruses or other pathogens are transferred from one surface to another, typically via cleaning cloths, mops or hands. Using the same cloth to clean a toilet and then a kitchen worktop is a classic example. Colour-coded systems prevent this by assigning specific cloths to specific areas.

What is the colour-coding system for cleaning?

The standard UK colour-coding system uses: Red for bathrooms and toilets, Blue for general low-risk areas like offices, Green for food preparation and kitchen areas, and Yellow for clinical and isolation areas. This prevents cloths being used across different risk zones.

How long should sanitiser be left on a surface?

Most sanitisers require a contact time of 1-5 minutes to achieve effective pathogen reduction. For a 99.9% kill rate, 5 minutes contact time is standard. The surface must remain visibly wet for the entire contact period. Check the product label for specific requirements.

How often should I change cleaning cloths?

With a single-cloth system, change after every 3-4 surfaces to prevent spreading contamination. With colour-coded cloths, change when moving between zones or when the cloth becomes visibly soiled. Disposable cloths should be used once and discarded. In high-risk areas like kitchens, use a fresh cloth more frequently.

CleanCalcs

Cross-Contamination Risk Calculator

Assess cross-contamination risk for cleaning procedures and get recommendations.

Area Type

Area type

Current Cleaning Method

Current cleaning method

Contact Surfaces

Door handles, taps, switches, worktops etc.

Foot Traffic Level

Foot traffic level

How We Calculate This

This calculator assesses cross-contamination risk based on area type, cleaning method, number of contact surfaces and foot traffic.

Risk scoring

Risk score = area base risk x method factor x traffic factor x surface factor

Area risk: Kitchen 8, Bathroom 7, Medical 9, Office 3, Childcare 8
Method factor: Single cloth 1.5x, Colour-coded 0.7x, Disposable 0.4x
Traffic: Low 0.7x, Medium 1.0x, High 1.4x

Risk levels

Score 0-3: Low risk | Score 4-6: Medium risk | Score 7-10: High risk

Frequently Asked Questions

Related Calculators

PPE Cost Calculator

Calculate monthly and annual PPE costs for cleaning staff including gloves, masks, and protective equipment.

COSHH Dilution Calculator

Calculate correct dilution ratios for cleaning chemicals based on concentration and application type.

Hand Sanitiser Calculator

Calculate hand sanitiser station count and refill frequency for a premises.

Last updated: March 2026

All calculations are estimates. Always verify quantities and timings for your specific situation.