Inputs
Tip: start with conservative cycle times and 100% peak load, then refine.
- Dirty change, showers, airlocks, clean change, drying.
- Optional equipment, supervisor, medical, and wastewater space.
- Module estimate using your preferred container size.
Example Data Table
| Scenario | Workers | Peak Window | Cycle | Lanes | Showers Provided | Estimated Total Area |
|---|---|---|---|---|---|---|
| Small crew turnover | 20 | 30 min | 6 min | 1 | 4 | ~45–60 m² |
| Medium crew turnover | 40 | 30 min | 7 min | 2 | 10 | ~90–120 m² |
| High peak demand | 70 | 25 min | 8 min | 3 | 24 | ~160–210 m² |
These examples are illustrative only; your inputs determine final results.
Formula Used
WastewaterStorage = PeakWater × SafetyFactor
How to Use This Calculator
- Enter your shift headcount and the busiest change window.
- Set conservative cycle times for showers and changing stages.
- Choose lanes and per-person areas matching your PPE level.
- Enable optional rooms for equipment, monitoring, or first aid.
- Click Calculate to see results above the form.
- Use Download CSV/PDF to save and share outputs.
1) Why decon unit sizing matters on active sites
Decontamination units protect workers, the public, and downstream trades by controlling the transition from “dirty” to “clean” zones. Under-sizing increases queue time, drives shortcut behavior, and raises cross-contamination risk. Over-sizing wastes footprint, utilities, and setup costs. This calculator balances throughput, privacy options, and circulation allowances to estimate a practical area for planning, scheduling, and layout.
2) Throughput: linking people, time, and showers
Peak turnover is defined by how many people must pass through in a limited change window. If 40 workers may exit within 30 minutes, average demand is 1.33 people per minute. With a 7‑minute shower cycle, the unit needs roughly (40×7)/30 ≈ 9.3 shower positions, rounded up for reliability and split across lanes to reduce congestion.
3) Occupancy drives changing and drying space
Changing rooms are sized by simultaneous occupancy rather than total headcount. The calculator estimates occupancy using PeoplePerMinute × StageMinutes, then multiplies by area per person. For example, 1.33 people/min and 4 minutes of dirty change implies about 6 people present at once. Applying a circulation factor (often 1.20–1.35) adds aisles, door clearance, and supervision space.
4) Airlocks and optional rooms affect the footprint
Transition points typically include an entry airlock, a shower interface, and an exit airlock. These are essential for pressure control, signage, and PPE handling. Optional rooms—equipment storage, supervisor/monitor space, medical/first‑aid, and wastewater service—can add meaningful area but improve operations, compliance, and emergency readiness.
5) Water and wastewater planning for utilities
Water demand during peak is calculated from shower flow and water-on minutes, then wastewater storage is increased with a safety factor. This helps estimate tank/service area and highlights utility constraints early on. For higher-risk tasks, increase cycle time, improve segregation, and verify requirements with project safety plans and local regulations.
FAQs
1) How do I choose the peak change window?
Use the shortest realistic period when most workers will decon, often shift end or a break. If uncertain, start with 20–30 minutes and adjust after observing actual queues.
2) Should I size showers for the full cycle or water-on time?
Size showers using full cycle time (entry, wash, exit, reset). Use water-on time only for utility planning so you do not under-provide shower positions.
3) What circulation factor should I use?
For tight units, use 1.20. For higher PPE, more supervision, or wheelchair access, use 1.30–1.40. Increase further if you have wide aisles or equipment staging.
4) When should I enable separate gender changing?
Enable it when privacy requirements apply and you cannot schedule separate usage. It duplicates changing and drying areas, but it can reduce conflict and improve compliance.
5) Do lanes replace extra showers?
No. Lanes spread traffic, reduce bottlenecks, and improve flow, but shower count is still driven by peak people, cycle minutes, and the peak window.
6) How is wastewater storage estimated?
Peak water equals peak people × shower flow × water-on minutes. Storage then applies a safety factor for surges, tank ullage, and operational buffer. Confirm disposal capacity and treatment requirements.
7) Is this calculator suitable for final design?
It is a planning tool for early layouts and budgeting. Final design should confirm ventilation, pressure regimes, egress, accessibility, contamination controls, and any project-specific standards.