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Sqratch Tools / MEP Systems / Air Changes Per Hour (ACH)

Air Changes Per Hour (ACH)

Calculate the ACH rate for ventilation systems based on room volume and fan CFM.

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Basis & Assumptions

  • ACH = (CFM × 60) ÷ Room Volume in Cubic Feet.
  • ASHRAE standards dictate minimum ACH values depending on room use (e.g., kitchens, hospitals, residential).

For quick design checks and study — not a substitute for your local Development Control Regulations, NBC provisions, or a licensed professional's judgement. Always verify against the bye-laws that apply to your site.

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