🔄 Air Changes Per Hour
💨 Pressurization Offset
Sizing Breakdown
Full Calculation Table
| Component | Basis | Value | Result |
|---|
How to Use the Hospital HVAC Calculator
Choose the hospital space type closest to your project for typical air change rate and pressurization direction, or select Custom for a specific project requirement.
Enter floor area and ceiling height to establish room volume, which drives supply and exhaust airflow together with the air change rate.
Enter the estimated gap area around doors and penetrations, used to calculate the pressurization offset needed between the room and corridor.
Click Calculate Hospital HVAC to see total supply airflow, exhaust airflow, and the offset airflow needed to maintain the required pressurization direction.
Understanding Hospital HVAC Design
Hospital HVAC systems serve two purposes at once: general comfort conditioning and infection control through carefully managed air change rates and pressurization. Unlike most commercial spaces, a hospital room's mechanical design is driven as much by clinical risk management as by thermal comfort, which is why Canadian healthcare facilities follow CSA Z317.2 guidance for mechanical requirements by room type.
| Room Type | Typical ACH | Pressurization | Recirculation |
|---|---|---|---|
| Operating Room | 20–25 | Positive | Limited, HEPA-filtered |
| Airborne Infection Isolation | 12 | Negative | Not permitted, dedicated exhaust |
| Protective Environment | 12 | Positive | Not permitted, dedicated supply |
| Emergency / ICU | 6–10 | Negative or neutral | Facility-policy dependent |
| General Patient Ward | 6 | Neutral | Typically permitted |
Values are general representative guidance for Canadian healthcare facilities. Confirm exact requirements against the current edition of CSA Z317.2 and your facility's specific infection control policy, which may exceed the code minimum for particular procedures or patient populations.
Positive vs. Negative Pressure: Protecting the Patient or Protecting Everyone Else
A positive pressure room, like an operating room or protective environment room for immunocompromised patients, keeps air flowing outward into the corridor whenever the door opens, so contaminants from outside cannot enter the clean space. A negative pressure room, used for airborne infection isolation, does the opposite: it keeps air flowing inward from the corridor so pathogens generated by the patient cannot escape into the hallway or adjacent rooms. Getting this direction right, and keeping it stable over time rather than just at initial handover, is exactly what a commissioning checklist is meant to verify before a room goes into clinical use.
How This Calculator Estimates Pressurization Offset
The pressurization offset is the difference between supply and exhaust airflow needed to push air in the required direction through door and penetration leakage paths. This calculator uses a simplified orifice flow relationship based on your specified door leakage area and the target pressure differential for the selected room type, similar to the approach used in the building pressurization calculator for broader building-level pressure control.
Operating Room Unidirectional Airflow
Beyond the total air change rate, operating rooms typically deliver a portion of their supply air through a unidirectional or laminar flow array positioned directly over the surgical field, creating a clean air curtain that sweeps contaminants away from the incision site before they can settle. The final filtration stage in that supply path is almost always HEPA, and the HEPA filter calculator can help work through that stage's sizing separately. This calculator estimates total supply airflow at the room level; the specific unidirectional array design and its airflow pattern require dedicated surgical suite design expertise beyond a general sizing tool.
Continuous Monitoring and Alarming
Given the infection control consequences of a pressurization failure, most Canadian jurisdictions require continuous monitoring and alarming of pressure differential for airborne infection isolation rooms and similar critical spaces, not just a one-time commissioning verification, a requirement echoed in the Public Health Agency of Canada's guidance on ventilation monitoring for isolation rooms. Confirm your specific facility's monitoring requirements with the local authority having jurisdiction and infection control team before finalizing the mechanical design.
Frequently Asked Questions
Operating rooms in Canadian hospitals typically require 20 to 25 total air changes per hour under CSA Z317.2 guidance, with a portion of that airflow delivered through a unidirectional or laminar flow ceiling array directly over the surgical field to minimize airborne contamination at the incision site.
A positive pressure room, sometimes called a protective environment room, keeps air flowing out of the room into the corridor to protect an immunocompromised patient from contaminants entering from outside. A negative pressure room, used for airborne infection isolation, keeps air flowing into the room from the corridor so that airborne pathogens from the patient cannot escape into adjacent spaces.
CSA Z317.2 and related Canadian guidance typically call for a minimum pressure differential of 2.5 pascals between an isolation room and the adjacent corridor, verified with the door closed. This differential needs to be continuously monitored and alarmed in most Canadian jurisdictions for airborne infection isolation rooms, given the infection control consequences of a pressurization failure. See the building pressurization calculator for broader pressure control beyond individual isolation rooms.
Isolation rooms and operating rooms generally require dedicated exhaust that is not recirculated to other spaces, since the entire purpose of the pressurization strategy is to control contaminant movement between the room and adjacent areas. General patient wards without isolation requirements may use more conventional recirculating systems, though hospital-wide infection control policy ultimately governs specific recirculation decisions.
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