MRS Mold Identification and Assessment 3 — Questions and Answers
Question 1: Which condition best describes the relative humidity level above which most indoor molds begin to grow?
- Above 30%
- Above 60% (Correct answer)
- Above 80%
- Above 95%
Correct answer: Above 60%
Most indoor mold species begin to colonize surfaces when sustained relative humidity exceeds 60%, with growth accelerating above 70%.
Question 2: What is the significance of finding Chaetomium species during a mold assessment?
- It indicates a clean, low-moisture environment
- It is a strong indicator of past or ongoing chronic water damage (Correct answer)
- It is the most common outdoor mold with little significance indoors
- It signals contamination from food storage areas only
Correct answer: It is a strong indicator of past or ongoing chronic water damage
Chaetomium thrives on wet cellulose and is rarely found outdoors in significant quantities, making its indoor presence a reliable indicator of water damage.
Question 3: During visual inspection, what does 'efflorescence' on a concrete wall indicate regarding mold risk?
- Active mold growth is present on the surface
- Water is migrating through the concrete, creating moisture conditions favorable to mold (Correct answer)
- The concrete has been properly waterproofed
- Mold remediation was previously performed
Correct answer: Water is migrating through the concrete, creating moisture conditions favorable to mold
Efflorescence is salt deposits left behind as water moves through concrete, indicating moisture intrusion that can support mold growth on adjacent organic materials.
Question 4: What type of sampling should a mold assessor collect when mold is suspected inside a wall cavity without opening the wall?
- Bulk sample of drywall paper
- Wipe sample of the wall surface
- Air sample from a small drilled hole into the cavity (Correct answer)
- Tape lift from baseboard trim
Correct answer: Air sample from a small drilled hole into the cavity
Drilling a small hole and drawing air from within the cavity allows spore trap sampling to detect mold without destructive opening of the wall.
Question 5: Which document provides widely referenced federal guidance on mold investigation and remediation in homes and buildings?
- OSHA 29 CFR 1910.1000
- EPA Publication 402-K-02-003 'Mold Remediation in Schools and Commercial Buildings' (Correct answer)
- NFPA 921 'Guide for Fire and Explosion Investigations'
- ASHRAE 62.1 'Ventilation for Acceptable Indoor Air Quality'
Correct answer: EPA Publication 402-K-02-003 'Mold Remediation in Schools and Commercial Buildings'
The EPA publication 'Mold Remediation in Schools and Commercial Buildings' is the primary federal guidance document for mold investigation and remediation practices.
Question 6: When comparing Aspergillus and Penicillium spores under a microscope, why are they often reported together as 'Aspergillus/Penicillium'?
- They always grow in the same colonies
- Their spores are morphologically identical and cannot be distinguished by standard microscopy (Correct answer)
- They both produce the same mycotoxins
- Laboratory regulations require reporting them together
Correct answer: Their spores are morphologically identical and cannot be distinguished by standard microscopy
Aspergillus and Penicillium spores are indistinguishable by optical microscopy and are therefore grouped together in spore trap analysis reports.
Question 7: What is the recommended action when a mold assessor finds visible mold growth covering more than 100 square feet?
- The homeowner can clean it with bleach without professional help
- It qualifies as a large contamination area requiring professional remediation per EPA guidance (Correct answer)
- Only the visible portion requires treatment
- Air sampling alone is sufficient to address the problem
Correct answer: It qualifies as a large contamination area requiring professional remediation per EPA guidance
EPA guidance classifies mold contamination exceeding 100 square feet as a large area requiring professional remediation with full containment protocols.
MRS Mold Identification and Assessment 3
Which condition best describes the relative humidity level above which most indoor molds begin to grow?