MRS Post-Remediation Verification 3 — Questions and Answers
Question 1: When comparing indoor post-remediation air samples to outdoor control samples, which outcome indicates successful remediation?
- Indoor counts are equal to or lower than outdoor counts for the same genera (Correct answer)
- Indoor counts are exactly 50% of outdoor counts
- No Cladosporium spores are detected indoors
- Indoor counts are below 500 spores/m³ regardless of outdoor levels
Correct answer: Indoor counts are equal to or lower than outdoor counts for the same genera
Successful remediation is confirmed when indoor spore concentrations are at or below outdoor background levels for the same fungal genera.
Question 2: What is the purpose of taking an outdoor 'control' or 'background' air sample during post-remediation verification?
- To measure the effectiveness of the containment barriers
- To establish a local ambient fungal baseline for comparison (Correct answer)
- To identify which mold species originated outdoors
- To comply with OSHA air quality regulations
Correct answer: To establish a local ambient fungal baseline for comparison
The outdoor control sample provides the ambient fungal baseline specific to that day and location, allowing meaningful comparison to indoor levels.
Question 3: A remediator performs post-remediation verification and finds no visible mold but air samples show elevated Aspergillus levels. What is the MOST likely explanation?
- The laboratory made an error in analysis
- Hidden or inaccessible mold colonies are still present (Correct answer)
- Aspergillus is always elevated in older buildings
- HVAC filters are releasing previously captured spores
Correct answer: Hidden or inaccessible mold colonies are still present
Elevated air counts without visible mold often indicate hidden contamination behind walls, ceilings, or in HVAC systems that was not fully remediated.
Question 4: Which laboratory analysis method provides identification of mold to the species level, not just genus?
- Spore trap microscopy
- PCR (polymerase chain reaction) analysis (Correct answer)
- Air-O-Cell cassette count
- Gravimetric dust sampling
Correct answer: PCR (polymerase chain reaction) analysis
PCR analysis detects specific DNA sequences, allowing identification of mold to the species level with greater precision than microscopy alone.
Question 5: How long should HVAC systems typically remain off before collecting post-remediation air samples?
- 30 minutes
- 1 hour
- 4–24 hours (Correct answer)
- No shutdown is necessary
Correct answer: 4–24 hours
HVAC systems should typically be shut off for 4–24 hours before sampling to allow airborne spores to settle and reflect natural conditions.
Question 6: Post-remediation verification documentation should include all of the following EXCEPT:
- Chain of custody forms for all samples
- Laboratory analysis reports
- Before-and-after photographs
- The remediator's personal guarantee of mold-free conditions (Correct answer)
Correct answer: The remediator's personal guarantee of mold-free conditions
Professional documentation never includes personal guarantees; it relies on objective sample data, chain of custody records, and photographic evidence.
Question 7: Which area is most critical to sample during post-remediation verification when Stachybotrys was the primary contaminant?
- Surfaces adjacent to the remediated area (Correct answer)
- Outdoor environment only
- HVAC supply vents
- Flooring in unaffected rooms
Correct answer: Surfaces adjacent to the remediated area
Surfaces adjacent to the remediated area are critical because Stachybotrys can spread during disturbance, and cross-contamination must be ruled out.
MRS Post-Remediation Verification 3
When comparing indoor post-remediation air samples to outdoor control samples, which outcome indicates successful remediation?