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Ventilation Design Flashcards

7 cards from real HVAC practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

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  1. What is the typical CO2 setpoint used in demand-controlled ventilation systems as an indicator of adequate ventilation?

    Answer: 700 ppm above outdoor levels (≈1,100 ppm)

    A common DCV setpoint is 700 ppm above outdoor ambient (roughly 1,100 ppm total), which ASHRAE 62.1 associates with providing approximately 15 cfm per person.

  2. In a hospital, which area requires the highest number of air changes per hour (ACH) according to ASHRAE 170?

    Answer: Operating room

    Operating rooms require a minimum of 20 ACH total air (with at least 4 ACH outdoor air) per ASHRAE 170 to control surgical site infection risk.

  3. What is the purpose of a transfer air pathway between spaces in a ventilation design?

    Answer: To supply conditioned air directly to a space without ductwork

    Transfer air (via grilles, door gaps, or ducts) allows a space to receive ventilation air that passes through from an adjacent space, reducing the need for dedicated supply runs.

  4. When designing natural ventilation using stack effect, the driving force is created by:

    Answer: Temperature and density differences between indoor and outdoor air

    Stack effect is driven by the buoyancy difference between warmer, less-dense indoor air and cooler, denser outdoor air, creating airflow through low inlets and high outlets.

  5. Which ASHRAE standard governs ventilation requirements specifically for healthcare facilities?

    Answer: ASHRAE 170

    ASHRAE 170 'Ventilation of Health Care Facilities' sets specific ACH, pressure relationships, filtration, and humidity requirements for hospitals and clinics.

  6. What is the correct pressure relationship between a hospital isolation room (airborne infection isolation) and the adjacent corridor?

    Answer: Isolation room is negative relative to corridor

    Airborne infection isolation (AII) rooms are maintained at negative pressure relative to the corridor to prevent infectious airborne particles from escaping the room.

  7. Which ventilation design method uses tracer gas measurements to quantify how effectively fresh air reaches the breathing zone?

    Answer: Age-of-air measurement

    Age-of-air (or mean age of air) measurements using tracer gases like SF6 or CO2 quantify how long air takes to reach the breathing zone, indicating ventilation effectiveness.