CMI CMI HVAC Systems & Ventilation Inspection 1 — Questions and Answers
Question 1: Why are HVAC duct systems a critical concern during a mold inspection in a water-damaged building?
- Ducts can distribute mold spores throughout the entire building, contaminating previously unaffected areas (Correct answer)
- HVAC systems only affect outdoor air quality, not indoor
- Mold cannot grow inside metal ductwork due to the surface chemistry
- Ducts are only relevant if the building is older than 30 years
Correct answer: Ducts can distribute mold spores throughout the entire building, contaminating previously unaffected areas
HVAC ductwork can act as a distribution network for mold spores, spreading contamination from a localized source to all areas served by the system.
Question 2: Which component of a central air handling unit (AHU) is most prone to microbial growth due to perpetual moisture accumulation?
- Drain pan and cooling coil (Correct answer)
- Supply air plenum
- Outdoor air damper
- Duct insulation on supply lines
Correct answer: Drain pan and cooling coil
The drain pan and cooling coil are continuously exposed to condensate, creating ideal wet conditions for mold and bacterial growth within the AHU.
Question 3: What is the significance of a negative building pressure in relation to mold growth potential?
- Negative pressure causes infiltration of humid outdoor air through cracks, increasing moisture load and mold risk (Correct answer)
- Negative pressure dries out the building, preventing mold growth
- Negative pressure has no relationship to mold growth
- Negative pressure is only relevant in industrial settings
Correct answer: Negative pressure causes infiltration of humid outdoor air through cracks, increasing moisture load and mold risk
A negatively pressurized building draws in unconditioned, potentially humid outdoor air through envelope gaps, raising indoor moisture levels and creating conditions favorable to mold growth.
Question 4: When inspecting flexible ductwork in an attic, what mold-related concern is unique to this material compared to sheet metal ducts?
- Flexible duct liner can absorb moisture and harbor mold growth that is difficult to remediate (Correct answer)
- Flexible ducts never develop condensation because they are not rigid
- Flex ducts are antimicrobial by design and do not support mold
- Only the exterior of flexible ducts can become contaminated
Correct answer: Flexible duct liner can absorb moisture and harbor mold growth that is difficult to remediate
Flexible ductwork contains fibrous insulating liner that can absorb moisture and support mold colonization, and contaminated sections typically must be replaced rather than cleaned.
Question 5: What does a high-efficiency MERV 13 filter do to help prevent mold growth in an HVAC system?
- It captures a high percentage of airborne mold spores before they can settle on wet cooling coils (Correct answer)
- It eliminates the need for duct cleaning
- It reduces humidity by absorbing moisture from the air stream
- MERV ratings are only relevant to dust, not mold spores
Correct answer: It captures a high percentage of airborne mold spores before they can settle on wet cooling coils
MERV 13 filters capture particles in the 0.3–1.0 µm range at ≥75% efficiency, significantly reducing the mold spore load that reaches wet heat exchanger surfaces where colonization could occur.
Question 6: An inspector finds standing water in the condensate drain pan of a rooftop unit. What is the primary corrective action?
- Clear the drain line obstruction and slope the pan correctly to eliminate standing water (Correct answer)
- Add biocide tablets to the pan to kill any mold
- Seal the drain pan with waterproof coating
- Replace the entire AHU immediately
Correct answer: Clear the drain line obstruction and slope the pan correctly to eliminate standing water
Standing water in a drain pan indicates a clogged or improperly sloped drain; correcting the obstruction and ensuring proper drainage is the primary fix to eliminate the mold growth medium.
CMI CMI HVAC Systems & Ventilation Inspection 1
Why are HVAC duct systems a critical concern during a mold inspection in a water-damaged building?