HVAC Indoor Air Quality and Filtration 3 — Questions and Answers
Question 1: Which ASHRAE standard provides minimum ventilation rates for acceptable indoor air quality in commercial buildings?
- ASHRAE 90.1
- ASHRAE 62.1 (Correct answer)
- ASHRAE 55
- ASHRAE 15
Correct answer: ASHRAE 62.1
ASHRAE Standard 62.1 establishes minimum outdoor air ventilation rates and IAQ requirements for commercial and institutional buildings.
Question 2: High relative humidity indoors (above 60%) most directly encourages which IAQ problem?
- Increased radon entry
- Mold and mildew growth (Correct answer)
- Higher carbon monoxide production
- Elevated VOC off-gassing from furniture
Correct answer: Mold and mildew growth
Relative humidity above 60% creates conditions that promote mold and mildew growth on surfaces and inside duct systems.
Question 3: What is the function of a bypass humidifier in an HVAC system?
- It removes excess moisture from supply air
- It adds moisture to a portion of airflow diverted from the supply plenum across a water panel (Correct answer)
- It measures relative humidity and signals the thermostat
- It filters biological contaminants from return air
Correct answer: It adds moisture to a portion of airflow diverted from the supply plenum across a water panel
A bypass humidifier diverts a portion of warm supply air through a moistened evaporator pad and returns it to the return plenum, adding humidity to the circulated air.
Question 4: Sick Building Syndrome (SBS) is most directly associated with which HVAC-related cause?
- Excessively high supply air temperatures
- Inadequate ventilation and accumulation of indoor pollutants (Correct answer)
- Oversized cooling equipment causing short-cycling
- High static pressure in ductwork
Correct answer: Inadequate ventilation and accumulation of indoor pollutants
SBS symptoms — headaches, fatigue, and irritation — are most commonly linked to poor ventilation that allows indoor pollutants to accumulate.
Question 5: Which type of UV light system is installed in the HVAC return air stream to reduce airborne biological contaminants?
- UV-A germicidal coil irradiator
- In-duct UV-C air purifier (Correct answer)
- UV-B surface sterilizer
- Photovoltaic UV panel
Correct answer: In-duct UV-C air purifier
In-duct UV-C systems installed in the return airstream irradiate passing air to inactivate bacteria, viruses, and mold spores.
Question 6: What does the term 'source control' mean in the context of indoor air quality management?
- Controlling the HVAC system source of supply air
- Eliminating or reducing the pollutant at its point of origin (Correct answer)
- Using activated carbon to absorb odors at the return grille
- Adjusting outdoor air damper position to dilute contaminants
Correct answer: Eliminating or reducing the pollutant at its point of origin
Source control means addressing the IAQ problem at its origin — such as sealing radon entry points or using low-VOC materials — rather than diluting or filtering afterward.
Question 7: A technician measures a static pressure drop across a filter that is significantly higher than the manufacturer's rated clean pressure drop. What does this most likely indicate?
- The filter is the wrong MERV rating for this system
- The filter is loaded with captured particles and needs replacement (Correct answer)
- Duct leakage upstream of the filter
- The blower motor is running at too high a speed
Correct answer: The filter is loaded with captured particles and needs replacement
Elevated pressure drop across a filter compared to its clean baseline indicates accumulated dust and debris loading, meaning the filter should be replaced.
HVAC Indoor Air Quality and Filtration 3
Which ASHRAE standard provides minimum ventilation rates for acceptable indoor air quality in commercial buildings?