HVAC Ventilation Design 4

Question 1

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

Accepted Answer

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

Answer

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.

Question 2

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

Accepted Answer

Operating room

Answer

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.

Question 3

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

Accepted Answer

To supply conditioned air directly to a space without ductwork

Answer

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.

Question 4

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

Accepted Answer

Temperature and density differences between indoor and outdoor air

Answer

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.

Question 5

Which ASHRAE standard governs ventilation requirements specifically for healthcare facilities?

Accepted Answer

ASHRAE 170

Answer

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

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HVAC Ventilation Design 4