CMI HVAC Systems and Mold Growth 2

Question 1

An inspector discovers that an HVAC system is sized significantly oversized for the building load. How does this contribute to mold risk?

Accepted Answer

Oversized systems short-cycle, failing to run long enough to adequately dehumidify the air

Answer

Oversized systems cool the space rapidly and shut off before the refrigerant coil has run long enough to condense and drain significant moisture from the air. This short-cycling keeps indoor relative humidity elevated, which is the primary driver of mold growth. Longer, properly sized run cycles are needed for effective dehumidification.

Question 2

Mold growth on supply air diffusers near the ceiling is often caused by which phenomenon?

Accepted Answer

Cold supply air causing condensation on the diffuser face when room humidity is high

Answer

Cold supply air chills the metal diffuser face below the room air's dew point, causing water vapor to condense directly on the surface. Dust carried in the air adheres to the wet surface, providing nutrients for mold. This is a surface condensation problem driven by high indoor RH, not a duct or filter issue.

Question 3

Which NADCA standard provides guidelines for the assessment and cleaning of HVAC systems suspected of mold contamination?

Accepted Answer

NADCA ACR (Assessment, Cleaning and Restoration of HVAC Systems)

Answer

NADCA's ACR (Assessment, Cleaning and Restoration of HVAC Systems) is the industry-recognized standard specifically for evaluating and cleaning HVAC systems, including mold-contaminated ones. ASHRAE 62.1 addresses ventilation rates, IICRC S500 covers structural water damage, and EPA IAQ Tools for Schools is an educational framework — none are HVAC cleaning protocols.

Question 4

When inspecting a rooftop package unit, what is the primary concern related to mold growth from the unit casing seams and roof penetrations?

Accepted Answer

Water infiltration through failed seals introducing outdoor moisture directly into the unit and ductwork

Answer

Failed caulking or sealant at casing seams and roof penetrations allows rainwater and outdoor humid air to enter the unit and connected ductwork without passing through the dehumidification process. This moisture directly wets internal insulation and liner surfaces, creating ideal mold conditions. Refrigerant leaks, UV degradation, and thermal cracking are secondary concerns unrelated to moisture infiltration.

Question 5

A building inspector finds mold on the interior liner of a supply trunk that tested positive for Aspergillus and Penicillium. The best remediation approach per IICRC S520 is:

Accepted Answer

Remove and replace contaminated lined ductwork sections that cannot be effectively cleaned

Answer

IICRC S520 requires removal and replacement of porous materials like duct liner when they cannot be effectively cleaned because mold hyphae penetrate the substrate and cannot be fully eliminated. Biocide sprays and encapsulants are not acceptable standalone remediation methods per S520, and increasing the upstream filter rating does nothing to address existing colonization downstream.

(CMI) Certified Mold Inspector Practice Test

(CMI) Certified Mold Inspector Practice Test

CMI HVAC Systems and Mold Growth 2