| Scenario | Area type | Trades | Density | Dust | Separation | Hygiene | Final score | Level |
|---|---|---|---|---|---|---|---|---|
| Light exterior repairs | Exterior / open | 3 | 4 | Low | Full | 90% | 18.6 | Low |
| Interior fit-out (mixed) | Interior / open | 6 | 12 | Medium | Partial | 75% | 46.9 | Moderate |
| High dust, enclosed zone | Interior / enclosed | 10 | 18 | High | None | 55% | 82.3 | Critical |
This calculator converts each factor into a 0–100 risk value, where higher means worse. A weighted sum produces a base score:
- Low: 0 to 24.9
- Moderate: 25.0 to 49.9
- High: 50.0 to 74.9
- Critical: 75.0 to 100
- Walk the site and note area type, airflow, and barrier quality.
- Estimate crew mixing: trades, density, and shared tools frequency.
- Score controls honestly: cleaning rounds, PPE use, and hand hygiene.
- Add context modifiers for sensitive materials, adjacency, and moisture.
- Press Calculate risk, then prioritize the top drivers shown.
Managing cross contamination in active construction zones
Cross contamination typically occurs through three pathways: shared contact surfaces, mixed traffic routes, and airborne transfer from dust and uncontrolled airflow. This calculator converts those pathways into a 0–100 index so teams can compare scenarios consistently and document control improvements.
Operational exposure profile
Sites with 6–10 trades operating concurrently often see higher interface risk because handoffs, staging, and shared access points multiply touch events. Worker density above 15 people per 100 m² can increase mixing, especially near elevators, material hoists, and corridor pinch points.
Control effectiveness and measurable targets
Hygiene controls can be tracked using observation sampling. As a practical target, many projects aim for at least 85% PPE compliance and 80% hand hygiene compliance during peak activity. Increasing cleaning frequency from 2 to 6 rounds per shift can materially reduce the cleaning risk component in the weighted score.
Airflow and dust management
High dust tasks (cutting, grinding, sanding) can dominate the score if barriers and ventilation are weak. Adding local extraction with HEPA filtration, wet cutting, and pressure-managed containment helps reduce both airborne spread and tracking on boots, carts, and tools.
Zoning and separation performance
Full separation performs best when barriers are sealed, routes are clearly split, and transitions are controlled. Partial barriers with gaps often behave like shared space in busy periods. If adjacent critical areas are connected, the multiplier increases to reflect the higher consequence of transfer.
Example data for quick benchmarking
The table below shows a simple benchmark set you can copy into daily controls reviews.
| Inputs snapshot | Trades | Density | Cleaning | Hand | PPE | Expected level |
|---|---|---|---|---|---|---|
| Controlled interior fit-out | 6 | 12 | 5 | 80% | 90% | Moderate |
| Enclosed, high dust activities | 9 | 18 | 2 | 60% | 70% | High to Critical |
Use the calculator to test “what-if” changes, then lock targets into checklists and shift briefings.
1) What does a score of 60 mean?
A 60 indicates high risk conditions where contamination transfer is likely without stronger controls. Focus on the top drivers table, then improve separation, ventilation, cleaning, and compliance to reduce the score.
2) Which inputs usually affect the score most?
Dust level, separation quality, ventilation control, and shared tools often contribute the most. Hygiene and cleaning can also swing results significantly when compliance is below 75%.
3) How should worker density be estimated?
Count the average number of workers in the active zone and divide by the approximate floor area. Enter people per 100 m². Use peak periods if congestion is a recurring issue.
4) Why are multipliers used?
Multipliers reflect increased consequence and exposure sensitivity. Sensitive materials, connected critical areas, and wet work can amplify the impact of transfer, so the final score increases even if base conditions stay the same.
5) Can I use this for non-dust contamination?
Yes. Treat “dust” as a proxy for transferable contaminants (fine debris, residues, overspray). Adjust separation, shared tools, hygiene, and cleaning inputs to reflect how the specific contaminant moves across the site.
6) How often should the assessment be repeated?
Recalculate when the work phase changes, trades overlap differently, or controls are adjusted. Weekly updates work well for stable phases, while high-change fit-outs benefit from daily reviews.
7) What’s a practical improvement strategy?
Lower one driver at a time: improve barriers, add cleaning rounds, reduce tool sharing, and verify PPE and hand compliance. Re-run the calculator after each change to quantify the benefit.