Site Inspection Inputs
Example Inspection Data
| Site | Date | Units inspected | Units positive | Containers inspected | Positive containers | HI (%) | CI (%) | BI |
|---|---|---|---|---|---|---|---|---|
| Example Site A | 2026-02-04 | 120 | 6 | 210 | 14 | 5.00 | 6.67 | 11.67 |
| Example Site B | 2026-01-28 | 80 | 2 | 130 | 4 | 2.50 | 3.08 | 5.00 |
| Example Site C | 2026-01-21 | 150 | 15 | 260 | 32 | 10.00 | 12.31 | 21.33 |
Formula Used
- House Index (HI) = (Positive units ÷ Units inspected) × 100
- Container Index (CI) = (Positive containers ÷ Containers inspected) × 100
- Breteau Index (BI) = (Positive containers ÷ Units inspected) × 100
- Larval Density (LD) = Total larvae ÷ Positive containers
The calculator also builds a composite risk score for construction sites:
- Each index is normalized using a cap value (default caps: BI 50, HI 20, CI 50, LD 50).
- Normalized indices are combined with weights (BI, HI, CI, LD).
- An environment multiplier increases risk with rainfall, heat, water area, and delayed drainage.
- A mitigation factor reduces risk when controls are stronger.
How to Use This Calculator
- Inspect living areas, work zones, and water-holding containers.
- Record how many units and containers were checked.
- Count positives where larvae or pupae are present.
- Optionally add larvae totals, rainfall, temperature, and drainage delay.
- Click Calculate Index to view results above the form.
- Download a CSV or PDF report for audits and meetings.
- Empty, cover, or drill drainage holes in stored materials.
- Keep sumps, pits, and tanks screened or treated as required.
- After rainfall, run a focused inspection within 24 hours.
- Track the composite score weekly to confirm improvements.
Why breeding indices matter on active sites
Construction sites create temporary water storage: curing tanks, drums, buckets, blocked drains, elevator pits, and tire stacks. Even one positive container can seed emergence and complaints. A consistent index helps safety teams link observations to action plans, budgets, and accountability. Use fixed inspection routes and record zero findings each round.
Interpreting House, Container, and Breteau indices
House Index (HI) shows how widely breeding is distributed across inspected units. Container Index (CI) measures the percentage of inspected containers that contain larvae or pupae. Breteau Index (BI) reports positive containers per 100 inspected units, allowing comparisons between projects with different sizes, crews, and inspection coverage.
Using larval density to target high-output sources
Larval Density (LD) estimates larvae per positive container and highlights productivity. Two areas can share the same BI, yet one may hold heavy larvae loads in fewer sources. Recording LD supports targeted fixes, for example cleaning sump baskets, covering drums, draining trays, and filling depressions. When LD drops while BI stays stable, controls are working but new containers are still appearing.
Environmental drivers that elevate construction risk
Rainfall refills micro-habitats and flushes eggs into containers. Higher temperatures can shorten development time and increase biting activity. Standing-water area and days since drainage indicate how long water persists. The calculator applies an environmental multiplier so the composite score reflects site conditions, not inspection counts. Update rainfall and drainage fields after storms, pumping, or dewatering.
Controls, documentation, and continuous improvement
A control score summarizes practices such as weekly housekeeping rounds, container covers, pump schedules, drain maintenance, and permitted larvicide use. Exportable reports support toolbox talks, audits, and subcontractor accountability. Track HI, CI, BI, and the composite score together: aim for steady reductions over two to four weeks. If BI falls but HI rises, breeding is spreading; widen patrol areas. If HI falls but CI rises, focus on container management and storage discipline. Document corrective actions with dates, photos, and responsible names for closure.
FAQs
1) What does the breeding index measure?
It summarizes how many inspected units and containers show larvae or pupae, then converts those observations into HI, CI, and BI. The composite score adds environment and controls to support prioritization.
2) What should be counted as a container?
Count any item that can hold water for days: buckets, drums, tires, trays, pits, tanks, sumps, and blocked drains. Record only those you actually inspected during the round.
3) Can I calculate results without larvae totals?
Yes. LD becomes zero if no larvae total is entered, but HI, CI, and BI still calculate correctly. Add larvae totals when possible to distinguish high-output sources from minor findings.
4) How is the control measures score used?
The score reduces the composite risk when site practices are stronger. Use it to reflect drainage routines, covers, housekeeping checks, and permitted treatments. Keep scoring consistent across inspections for meaningful trends.
5) How often should inspections be completed?
Weekly is a practical baseline on most projects, with extra checks after rainfall, dewatering changes, or major material deliveries. Higher-risk zones such as pits and sumps may need daily visual checks.
6) What does the composite score range mean?
It scales from 0 to 100 and maps to Low, Moderate, High, or Critical bands. Use the band to set response urgency, then review the individual indices to identify where improvements are needed.