Slab Emission Risk Calculator

Why slab emissions matter in occupied buildings

Concrete slabs can release chemicals from curing compounds, adhesives, coatings, or moisture-related reactions. Even when the source is below flooring, emissions can migrate into the breathing zone and accumulate if ventilation is limited. Early screening helps teams decide whether sealing, purge ventilation, or material substitution is needed before handover.

Key parameters that control concentration

The most influential inputs are slab area, emission rate, room volume, and ventilation (ACH). Larger areas and higher rates increase the generation term, while greater airflow dilutes contaminants. Temperature and humidity can accelerate off‑gassing, so using operating conditions improves planning accuracy. A safety factor can be applied when field measurements are uncertain or when material variability is expected.

Interpreting risk levels for decision making

The calculated daily average concentration is compared to your selected threshold. Low results generally support routine monitoring, while moderate results often justify targeted ventilation improvements. High or critical outcomes indicate a need for controls such as sealing systems, dehumidification, or reduced occupancy until verification testing confirms acceptable levels.

Mitigation strategies that reduce emissions and exposure

Effective options include applying verified barrier sealants, selecting low‑emission flooring systems, increasing outdoor air rates, and managing humidity to limit chemical release. Post‑mitigation testing should be performed after cure time and before full occupancy. Document assumptions, product data, and site readings so future audits can trace the basis of decisions.

Worked example data for screening

Example: area 120 m², emission rate 1.50 mg/m²·hr, volume 300 m³, ACH 1.2, temperature 24°C, RH 55%, sealant reduction 20%, safety factor 1.2, outdoor background 0.02 mg/m³, threshold 0.30 mg/m³, exposure 10 hr/day. The model estimates a daily average concentration near 0.12 mg/m³, which is about 40% of the threshold and typically indicates low risk.

FAQs

1) What does the emission rate represent?

The emission rate is the contaminant mass released per slab area per hour. Use measured product data when available, or apply a conservative screening value if uncertainty is high.

2) Why is ventilation entered as ACH?

ACH captures how often indoor air is replaced each hour. Higher ACH increases dilution and typically lowers predicted concentration for the same slab source strength.

3) How do temperature and humidity affect results?

Warmer, more humid conditions can increase off‑gassing from coatings and adhesives. The calculator applies a screened adjustment factor to reflect higher emissions under harsher conditions.

4) When should I use a safety factor above 1.0?

Use a higher safety factor when inputs are estimated, material variability is unknown, or the space is sensitive. It provides a buffer to reduce under‑prediction during planning.

5) Can sealing always reduce emissions by the stated percentage?

No. Reduction depends on product selection, surface prep, cure, and continuity. Enter reductions only when a barrier system is specified and performance is supported by technical data.

6) Is the result a compliance determination?

No. This is a screening estimate to support decisions. For compliance, use a qualified IAQ plan, validated sampling methods, and professional interpretation against applicable standards.

7) What should I export for project records?

Export the inputs, threshold used, and key outputs such as daily average concentration and risk level. Attach supporting notes, product sheets, and any field measurements used.