MRS Containment & Isolation Procedures 2 — Questions and Answers
Question 1: What is the minimum number of polyethylene sheeting layers required for a critical barrier in a full containment setup?
- One layer of 4-mil sheeting
- Two layers of 6-mil sheeting (Correct answer)
- Three layers of 2-mil sheeting
- One layer of 10-mil sheeting
Correct answer: Two layers of 6-mil sheeting
Full containment critical barriers require two layers of 6-mil polyethylene sheeting to provide sufficient durability and vapor resistance.
Question 2: When constructing an airlock for a containment zone, what is the purpose of the inner flap overlap?
- To increase air circulation within the containment
- To create a pressure differential that prevents spore escape (Correct answer)
- To reduce the need for negative air machines
- To allow equipment to pass through more easily
Correct answer: To create a pressure differential that prevents spore escape
Overlapping inner flaps maintain the pressure differential by preventing a direct open path between the contaminated zone and the clean area.
Question 3: A technician discovers that the HVAC system services both the containment area and adjacent clean rooms. What is the correct action?
- Increase negative air machine output to compensate
- Seal all HVAC registers inside and near the containment zone (Correct answer)
- Run the HVAC at low speed during remediation
- Install HEPA filters on the HVAC return
Correct answer: Seal all HVAC registers inside and near the containment zone
All HVAC registers within and adjacent to the containment must be sealed to prevent cross-contamination through the duct system.
Question 4: Which factor most directly determines whether a project requires mini containment versus full containment?
- The species of mold identified
- The total square footage of affected material (Correct answer)
- The building owner's preference
- The ambient outdoor temperature
Correct answer: The total square footage of affected material
IICRC S520 and EPA guidelines use the size of the affected area (typically 10 sq ft cutoffs) to determine the required containment level.
Question 5: During active mold remediation, what is the recommended air pressure differential inside a full containment relative to the surrounding area?
- -0.01 to -0.02 inches of water column
- -0.05 to -0.10 inches of water column (Correct answer)
- +0.01 to +0.02 inches of water column
- Zero differential (neutral pressure)
Correct answer: -0.05 to -0.10 inches of water column
A negative pressure of -0.02 to -0.05 inches of water column (some references cite up to -0.1 in.wc) ensures air flows inward, preventing spore migration outward.
Question 6: What should a remediator do if a critical barrier poly sheet is accidentally torn during remediation work?
- Continue work and patch the tear at end of day
- Stop work immediately, seal the tear with tape, and assess air quality (Correct answer)
- Increase exhaust fan speed and continue
- Notify the building owner and await instructions before continuing
Correct answer: Stop work immediately, seal the tear with tape, and assess air quality
Any breach in the critical barrier must be repaired immediately to restore containment integrity before work continues.
Question 7: When using a negative air machine (NAM) to maintain containment, where should the exhaust duct discharge?
- Back into the same room to recirculate air
- Into an adjacent clean room to dilute contaminants
- To the building exterior or a location away from HVAC intakes (Correct answer)
- Into the building's existing HVAC return
Correct answer: To the building exterior or a location away from HVAC intakes
NAM exhaust must discharge outdoors, away from HVAC intakes and building openings, to prevent re-entry of contaminated air.
MRS Containment & Isolation Procedures 2
What is the minimum number of polyethylene sheeting layers required for a critical barrier in a full containment setup?