HVAC Indoor Air Quality and Filtration 5 — Questions and Answers
Question 1: When performing an IAQ investigation, which instrument measures airborne particulate matter concentration?
- Manometer
- Psychrometer
- Particle counter (Correct answer)
- Combustion analyzer
Correct answer: Particle counter
A particle counter measures the number and size distribution of airborne particles per cubic foot or cubic meter of sampled air.
Question 2: What is the term for the condition where chemical contaminants from one area migrate into another area through HVAC ductwork or building pressurization?
- Cross-contamination (Correct answer)
- Thermal bridging
- Entrainment
- Recirculation
Correct answer: Cross-contamination
Cross-contamination occurs when airborne pollutants from one zone — such as a copy room or lab — migrate through shared HVAC systems into occupied spaces.
Question 3: Which ASHRAE standard covers residential ventilation requirements, including whole-house mechanical ventilation?
- ASHRAE 62.1
- ASHRAE 62.2 (Correct answer)
- ASHRAE 90.2
- ASHRAE 55
Correct answer: ASHRAE 62.2
ASHRAE 62.2 specifically addresses ventilation and IAQ requirements for low-rise residential buildings, including whole-building and local exhaust strategies.
Question 4: A technician finds microbial growth on cooling coil surfaces. Besides cleaning the coil, what HVAC design factor should be corrected to prevent recurrence?
- Increase supply air temperature to reduce condensation
- Ensure the drain pan slopes properly and condensate drains freely (Correct answer)
- Replace the compressor to lower suction pressure
- Increase blower speed to reduce coil contact time
Correct answer: Ensure the drain pan slopes properly and condensate drains freely
Standing water in improperly draining condensate pans provides the moisture environment that sustains biological growth on cooling coils.
Question 5: What does the term 'dilution ventilation' mean in IAQ practice?
- Filtering pollutants using activated carbon before recirculation
- Introducing outdoor air to reduce indoor contaminant concentrations (Correct answer)
- Pressurizing a space to prevent pollutant infiltration
- Using UV light to neutralize biological contaminants in recirculated air
Correct answer: Introducing outdoor air to reduce indoor contaminant concentrations
Dilution ventilation reduces indoor pollutant concentrations by mixing clean outdoor air with contaminated indoor air until acceptable levels are achieved.
Question 6: Which action is most effective at reducing volatile organic compounds (VOCs) introduced by new building materials during initial occupancy?
- Installing UV-C lamps in the ductwork
- Conducting a flush-out with 100% outdoor air at maximum ventilation rates before occupancy (Correct answer)
- Adding a MERV 16 mechanical filter
- Sealing all duct joints with mastic
Correct answer: Conducting a flush-out with 100% outdoor air at maximum ventilation rates before occupancy
A pre-occupancy flush-out using maximum outdoor air flow rates purges VOCs off-gassed by new materials before building occupants are exposed.
Question 7: What is the primary limitation of portable air purifiers with HEPA filtration in large commercial spaces?
- They produce harmful ozone as a byproduct
- Their airflow capacity (CFM) is too low to adequately clean the air volume of large spaces (Correct answer)
- They remove beneficial negative ions from indoor air
- They only capture particles larger than 10 microns
Correct answer: Their airflow capacity (CFM) is too low to adequately clean the air volume of large spaces
Portable HEPA units have limited CFM ratings designed for room-scale spaces, and multiple units or whole-building HVAC integration is required for larger commercial environments.
HVAC Indoor Air Quality and Filtration 5
When performing an IAQ investigation, which instrument measures airborne particulate matter concentration?