Allergen Reduction Calculator for Construction Work Zones

Work zone allergen sources and exposure pathways

Construction allergens commonly rise from drywall dust, wood fibers, insulation fragments, and settled debris re-suspended by foot traffic. Fine particles penetrate deeper into occupied areas, especially when barriers leak or doors are frequently opened. Establishing a baseline concentration (C0) and background level (Co) helps separate job-generated load from building-wide conditions.

Inputs that drive the reduction model

The calculator uses zone volume (area × height), ventilation rate (ACH), filtration airflow, filter efficiency, deposition rate, and source reduction. Ventilation converts to an equivalent clean-air flow (Qv = ACH × V). Filtration converts to clean-air delivery (Qf = airflow × efficiency). Source reduction represents containment, wet methods, and housekeeping that lower the effective starting level.

Interpreting clean-air delivery and removal rate

Total clean-air flow is Qv + Qf. Dividing by volume yields the clean-air intensity, which drives the exponential decay rate. Deposition (kdep) adds removal from settling and surface capture. Higher k shortens the time needed to reach a target, but diminishing returns appear once leakage and background dominate. Use the score as a comparative indicator across scenarios.

Setting realistic targets for shift planning

Targets should be above background unless background is reduced first. For active demolition, practical planning often aims for stronger controls: 4–8 ACH and additional portable filtration sized to the zone, with higher airflow placed inside containment. If time-to-target exceeds the planned task window, increase Qf, tighten barriers, or raise source reduction through wet cutting and vacuum extraction.

Documentation and control verification on site

Use the download reports to brief supervisors, record assumptions, and track improvements over time. Validate inputs with airflow measurements, ventilation balancing notes, and spot readings from particle or allergen monitoring. Update C0 after major task changes. Combine this model with signage, PPE, and cleaning schedules to maintain consistent conditions through the workday. When selecting filters, match efficiency to the nuisance fraction; 95% and above supports dust control. If multiple units run, sum airflow to estimate combined Qf and compare alternatives consistently across different layouts.

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FAQs

1) What does background Co represent?

It is the lowest steady level you can achieve without changing outside or building-wide conditions. If Ct is set below Co, the model cannot reach it until background sources are reduced.

2) How should I choose filter airflow and efficiency?

Use the manufacturer airflow at the intended setting and apply an efficiency appropriate for the particle size range. For multiple units, add airflow totals and use the same efficiency assumption for consistent comparisons.

3) Why does the calculator say the target is not feasible?

This occurs when the target is below the background, when starting and background levels are nearly equal, or when removal is very low. Increase clean-air delivery, improve containment, or revise targets to realistic values.

4) Can I use this for multiple rooms?

Yes. Run separate scenarios per zone because volume, leakage, and equipment placement differ. For connected areas, treat them as one larger volume only if airflow mixing between rooms is unrestricted.

5) What is a practical ACH range for renovation work?

Planning often starts around 4–8 ACH for occupied-adjacent work zones. Higher rates may be needed for dusty tasks or small containments, but confirm with measured airflow and pressure control.

6) Does the reduction percent include source control?

Yes. Source reduction lowers the effective starting level before decay is applied. The reported reduction compares the final concentration to the original C0, so stronger containment and cleaning typically improves the percent reduction.