Inputs
Example Data Table
| Scenario | Area (m2) | Occupants | Hazard | Egress | Protection | Activity | Score | Category |
|---|---|---|---|---|---|---|---|---|
| Office zone | 300 | 35 | 2 | 4 | 4 | 1.00 | 18.7 | Low |
| Workshop bay | 180 | 45 | 4 | 3 | 3 | 1.30 | 61.5 | High |
| Hot works area | 120 | 30 | 5 | 2 | 2 | 1.60 | 86.2 | Critical |
Use this table to benchmark your site zones and decide where controls matter most.
Formula Used
First compute occupancy density: Density = Occupants / Area(m2). Each input is normalized to a 0-1 scale.
The weighted base score is: Base = 0.22*Occ + 0.22*Haz + 0.15*Dur + 0.12*Egr + 0.12*Prot + 0.10*Inc + 0.07*Train.
Final risk score: Risk = 100 * Base * Activity, capped between 0 and 100. Higher egress and protection reduce risk through inverse scaling.
How to Use This Calculator
- Enter the occupied area and select the correct unit.
- Input expected occupants, including visitors during peak periods.
- Rate hazard severity, egress quality, and protection level from 1 to 5.
- Set exposure hours and activity factor for the work type.
- Add incident history and training coverage for the area team.
- Press Calculate Risk to view the score above the form.
- Download CSV or PDF to attach to permits and briefings.
Article
Why occupied area risk matters on active sites
Occupied zones combine people, equipment, and changing work fronts. When density rises, small issues like blocked walkways or poor visibility can escalate into delays, injuries, or evacuation failures. Using a consistent score helps supervisors compare zones and document decisions for briefings, permits, and audits.
Key inputs that drive the score
The calculator blends occupancy density, hazard severity, exposure duration, egress quality, protection level, incident history, and training coverage. Higher egress and protection reduce the score because they improve escape time and response capability. An activity factor accounts for tasks that increase ignition, pinch points, or conflict with traffic routes.
Interpreting categories and taking action
Low and Moderate results typically support routine controls: housekeeping, signage, and toolbox talks. High results often justify zoning, staggered access, and additional inspections. Critical results indicate the area should be restricted until layout and protection improvements are in place and verified.
Example data to validate your assumptions
Use the sample below to sanity check inputs before applying the method to multiple zones. As a quick benchmark, density above 0.50 persons per m2 is treated as crowded for normalization, so reducing occupants or increasing usable area can quickly lower risk.
| Input | Example value | Notes |
|---|---|---|
| Area | 250 m2 | Defined occupied footprint for the zone |
| Occupants | 40 | Include visitors during peak access |
| Hazard severity | 3 | General construction hazards present |
| Egress quality | 3 | Routes exist but require monitoring |
| Protection level | 3 | Basic protection with planned checks |
| Activity factor | 1.20 | Moderately elevated activity and interaction |
Good practice for records and continuous improvement
Recalculate when crew size changes, access routes shift, or high-risk tasks start. Store CSV or PDF outputs with daily permits and pre-task plans. Track incident counts per zone and raise training coverage to reduce the normalized training component over time.
FAQs
1) What does the risk score represent?
The score is a 0-100 index combining density, hazards, exposure, egress, protection, incidents, and training. It helps compare areas consistently and prioritize practical controls.
2) Is this a replacement for formal safety assessments?
No. It supports quick screening and documentation. Use it alongside site-specific procedures, permits, and any required regulatory or client risk assessment processes.
3) How should I choose hazard severity?
Rate 1 for minor hazards and 5 for severe hazards such as hot works, heavy lifts, energized systems, or confined access. Be consistent across zones for comparison.
4) Why do higher egress and protection reduce the score?
Better exits and protection improve evacuation speed and emergency response capability. The calculator inversely scales these inputs to reflect their risk-reducing effect.
5) What activity factor should I use?
Use 1.0 for normal operations, 1.2-1.5 for congested or interactive tasks, and up to 2.0 for high-risk activities. Apply the same logic to similar work packages.
6) How often should I update the calculation?
Update whenever occupancy, layout, or work type changes. A good minimum is daily for active zones and before any shift with unusual access or task complexity.
7) Can I use it for multiple zones on one project?
Yes. Run each zone separately, save the CSV outputs, and compare categories. This supports zoning decisions, staffing plans, and targeted inspections.