Calculate Air Changes Per Hour (ACH) for Your Space
For specific air changes per hour calculations; adjust the room dimensions to match your own (If the calculator did not load, please refresh your page).
MedicAir® Air Changes Per Hour Calculator
The MedicAir® is a medical-grade HEPA air purifier that is extremely easy to maintain with a simple swap of a single all-in-one cartridge housing a HEPA H13 Filter, Activated Carbon Filter, and Ultra-Violet Type-C light. The MedicAir® is used in thousands of medical offices, and commercial offices, globally.
What is the ACH calculator for?
The ACH (Air Changes Per Hour) calculator helps determine how often the air inside a room is replaced or filtered by your air purifier, HVAC system, or ventilation setup. This is essential for maintaining indoor air quality in homes, offices, medical clinics, and schools.
Originally popularized during COVID-19 for air purifiers, ACH is now a critical metric in choosing effective ventilation. This tool uses room volume and your air purifier’s CADR (Clean Air Delivery Rate) to calculate ACH — a key factor in reducing airborne contaminants.
The calculation is based on the size of the room, ceiling height, width, and length in feet to calculate the ACH. For simplicity, the calculations and breakdowns of cubic feet per minute, CFM variable adjustments, and HVAC-related ventilation rates are not shown or used.
What is the recommended ACH, Air Changes Per Hour?
🔹 Medical Environments (Hospitals, Clinics, Labs): Recommended ACH is 10+ air changes per hour
🔹 Commercial & Office Spaces: Recommended ACH is 5–6 air changes per hour
🔹 Homes & Residential Spaces: ACH of 4–6 is typically sufficient for bedrooms, living rooms, and kitchens
📌 Higher ACH is recommended for allergy sufferers, those with respiratory conditions, or during flu season.
Calculating Air Changes Per Hour (ACH):
Measure the volume of your room
Multiply:Length (ft) x Width (ft) x Ceiling Height (ft)
➤ Example:25 ft x 20 ft x 8 ft = 4,000 cubic feetConvert CADR to CFH (Cubic Feet per Hour)
➤ Example:CADR 605 x 60 = 36,300 CFHCalculate ACH using this formula
➤ACH = CFH ÷ Room Volume
➤ACH = 36,300 ÷ 4,000 = 9.075
Air Changes Per Hour - Frequently Asked Questions (FAQ)
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ACH stands for Air Changes Per Hour. It refers to how many times the air within a defined space is completely replaced in one hour by an air purifier, HVAC system, or ventilation system.
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A higher ACH rate means your indoor air is filtered or replaced more frequently, reducing airborne contaminants like dust, allergens, viruses, and odors. This is critical in medical offices, schools, and homes with allergy sufferers.
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Residential bedrooms or offices should have at least 4–6 ACH. Medical clinics and dental offices should target 10–12 ACH or higher for optimal protection.
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Measure your room size (length × width × height), convert your air purifier’s CADR to cubic feet per hour (CFM × 60), and divide that number by the room volume. This gives your ACH.
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CFM (Cubic Feet per Minute) is a general airflow measurement, while CADR (Clean Air Delivery Rate) measures the volume of filtered air. CADR is better for assessing air purifier performance.
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Yes and no — ACH is based on room volume. Air purifiers are most effective when used in a closed space. To achieve the right ACH, you should calculate for each room individually, however our air purifiers are powerful enough for most homes.
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To maintain your target ACH, your air purifier should run continuously or on a smart sensor mode that adjusts speed based on real-time air quality.
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Yes — commercial and residential HVAC systems have ventilation rates that contribute to overall ACH. Combining HVAC and air purifiers helps reach optimal ACH levels.
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No — ACH refers to how often air is replaced or filtered, while ventilation involves bringing in fresh outdoor air. Both improve indoor air quality but serve different functions.