Cleanroom & Contamination Control worked example

Cleanroom Air Changes at 72% share of room volume served by this air-change scenario: a worked example

Here is what the math looks like when conditions slip. We hold every other input steady and drop share of room volume served by this air-change scenario to 72%, then walk the calculation through step by step. Estimate cleanroom air-change airflow load from room volume, target ACH, room share, and fixed makeup-air allowance.

The inputs for this scenario

  • Cleanroom room volume: 18,000 ft³ (held at the documented default)
  • Target air changes per hour: 45 ACH (held at the documented default)
  • Share of room volume served by this air-change scenario: 72 % (the input this scenario stresses; the baseline uses 100)
  • Fixed makeup-air or leakage allowance: 2,500 ft³/h (held at the documented default)

Working through the calculation

  • The calculation starts from the formula this tool documents: Recirculated air-change load = cleanroom room volume × target air changes per hour × room volume served by this air-change scenario.
  • Cleanroom air-change airflow load works out to 585,700 cleanroom air-change airflow load at these inputs, and this is the headline figure for the scenario.
  • Air-change load per room ft³ works out to 32.54 $ / piece at these inputs.
  • Recirculated air-change load works out to 583,200 $ at these inputs.
  • Fixed makeup-air or leakage allowance works out to 2,500 $ at these inputs.

How this compares with the baseline

  • Against the tool's baseline example, where share of room volume served by this air-change scenario sits at 100% and the headline result is 812,500 cleanroom air-change airflow load, this scenario comes in 27.91% below the baseline at 585,700 cleanroom air-change airflow load.
  • The practical read: the gap between this scenario and the baseline is entirely attributable to share of room volume served by this air-change scenario, so recovering it is worth quantifying in dollars before considering equipment or staffing changes. It treats airflow as a simple volume-times-ACH figure and does not model unidirectional flow velocity, return path resistance, or cleanliness recovery dynamics, which a full CFD or recovery test would capture.

Results at a glance

  • Cleanroom air-change airflow load: 585,700 cleanroom air-change airflow load (headline result)
  • Air-change load per room ft³: 32.54 $ / piece
  • Recirculated air-change load: 583,200 $
  • Fixed makeup-air or leakage allowance: 2,500 $

Run it with your numbers

  • To rerun this with your own numbers, open the live Cleanroom Air Changes calculator, set share of room volume served by this air-change scenario to your actual value, and adjust the remaining inputs to match your operation.

Last reviewed 2026-05-12.