Room Air Cleaning Calculator

Room Air Cleaning Inputs

Use this for planning filtration and ventilation during interior work. Results assume well-mixed air; real conditions vary with layout, dust sources, and airflow patterns.

Example Data Table

Sample planning scenario for interior finishing work.

Your results will vary based on room geometry, leakage, and equipment placement.

Formula Used

• Room volume: V = L × W × H
• Cleaner air changes: ACH_clean = Q_clean / V (hour-based units)
• Total air changes: ACH_total = ACH_vent + ACH_clean
• Cleanup time (well-mixed): C/C0 = e^(−ACH_total·t)
• Time to remaining fraction r: t = −ln(r) / ACH_total

The cleanup model assumes uniform mixing and constant airflow.

How to Use This Calculator

• Measure room length, width, and height using one unit system.
• Enter existing ventilation as air changes per hour, if known.
• Enter the number of air cleaners and their clean-air capacity.
• Choose a cleanup percentage to estimate time-to-clean.
• Optionally set a target ACH to size equipment capacity.
• Press Submit to view results above, then export CSV or PDF.

For dusty tasks, consider source capture and containment too.

Practical Tips for Construction Indoor Air

• Seal doors, returns, and penetrations to limit dust migration.
• Place cleaners to promote circulation, not short-circuiting.
• Replace filters on schedule; clogged filters cut performance.
• Use negative pressure when isolating demolition or sanding.
• Confirm performance with particle counters when possible.

Worksite air challenges in enclosed rooms

During drywall sanding, demolition, and cutting, airborne dust rises quickly and can migrate through corridors and return ducts. Planning an air-cleaning rate helps protect adjacent trades, finishes, and sensitive tools, especially near occupied areas. This calculator converts room dimensions into volume, then links that volume to ventilation and filtration capacity so you can plan cleanup between activities and reduce lingering haze after high-dust steps.

Translating airflow into effective air changes

Air change rate combines outdoor air and filtered clean air. Ventilation ACH represents HVAC supply, exhaust, or intentional make-up air, and it may vary with doors open or closed during work. Cleaner ACH equals total clean-air delivery divided by room volume, using consistent hour-based units. Adding both values estimates an effective removal rate when air is reasonably mixed across the occupied zone.

Estimating clearance time with exponential decay

The clearance model assumes concentration decays exponentially. A 90% cleanup target leaves 10% of the starting level, while 99% leaves 1%. The calculator uses t = -ln(remaining fraction)/ACH_total and reports minutes to reach 90%, 95%, and 99% reduction. Higher targets require more time, so schedule sequencing and re-entry limits accordingly for crews and occupants on site.

Sizing equipment to hit a target ACH

When you set a target ACH, the tool back-calculates the clean-air delivery needed after accounting for existing ventilation. This supports selecting portable filtration units, sizing negative air machines, or deciding how many units to operate in parallel for large rooms and hallways. Compare required total CADR to equipment ratings, then adjust unit count or placement to meet the target reliably in practice.

Execution details that change real performance

Field results depend on airflow paths. Avoid short-circuiting by keeping unit intake away from its discharge and by promoting circulation with safe, low-velocity fans aimed across the space and away from fragile finishes. Seal door gaps and penetrations to limit dust migration, and use plastic barriers for containment. Replace loaded filters on schedule and verify outcomes with particle readings or smoke tests before removing isolation barriers. Document settings, airflow readings, and filter changes daily to support quality control, client communication, and repeatable results across phases project.

FAQs

1) What does CADR mean in this calculator?

CADR is the clean-air delivery rate from filtration. The calculator converts CADR into cleaner ACH using room volume, then combines it with ventilation ACH.

2) Why does 99% cleanup take much longer than 90%?

Cleanup follows exponential decay. Each additional percentage point removes a smaller remaining fraction, so high targets need more time at the same ACH.

3) Should I include HVAC ventilation if I am using containment?

Include any intentional supply or exhaust that actually exchanges air in the isolated zone. If vents are sealed, set ventilation ACH to near zero.

4) How do I estimate ventilation ACH if I do not know it?

Start with a conservative range, such as 0 to 2 ACH for closed rooms, then refine using airflow measurements or commissioning data.

5) Where should I place portable air cleaners?

Place units to promote circulation across the room without short-circuiting. Keep intakes away from clean exits and avoid blowing dust toward finished areas.

6) Are these results exact for every room?

No. Results assume well-mixed air. Obstructions, leaks, and poor placement reduce effectiveness, so verify with particle readings and adjust operation.