MRS Cheat Sheet 2026

The 30 highest-yield MRS facts, distilled from real exam questions. Print it, save it as a PDF, or study it here — free, no sign-up.

1. Which factor most directly determines whether a project requires mini containment versus full containment? → The total square footage of affected material
2. Which mold genus is most associated with causing invasive infections in immunocompromised individuals and warrants the highest worker caution? → Aspergillus
3. Which document provides widely referenced federal guidance on mold investigation and remediation in homes and buildings? → EPA Publication 402-K-02-003 'Mold Remediation in Schools and Commercial Buildings'
4. Which statement correctly describes how treated lumber (pressure-treated with preservatives) responds to mold? → Treated lumber resists decay fungi but can still support surface mold species
5. During remediation in an occupied building, negative pressure containment serves which CRITICAL secondary function beyond preventing spore spread? → Protecting building occupants from chemical cleaning agent vapors
6. Which of the following statements about HEPA filtration efficiency is correct? → HEPA filter efficiency increases as the filter loads with captured particles
7. In the context of IICRC S520, what is a mold remediation 'Protocol'? → A written document specifying the scope and procedures for remediation
8. Which standard of practice is MOST important for ensuring quality in HEPA Filtration & Air Scrubbing? → Following evidence-based protocols while adapting to specific circumstances
9. When a conflict arises between standard procedures and a unique situation in Personal Protective Equipment, what should a MRS professional prioritize? → Safety and ethical obligations while seeking expert consultation
10. When remediating mold in an occupied building, which document must be prepared and provided to occupants before work begins? → A written remediation plan or scope of work including relocation recommendations
11. During mold remediation, what should workers do before exiting the containment area? → Remove all PPE inside the containment and bag it
12. Which instrument measures the moisture content of air by comparing the readings of a wet-bulb and dry-bulb thermometer? → Sling psychrometer
13. When assessing mold on ceiling tiles, what property most determines whether cleaning or replacement is appropriate? → The porosity and absorbency of the tile material
14. What is the risk of reusing disposable N95 respirators across multiple mold remediation shifts? → Mold spores can accumulate and grow on the filter media, increasing exposure risk
15. A remediator encounters mold growing behind a bathtub surround on the framing. The tile itself shows no mold. What is the most likely cause? → Grout failure allowing water to migrate behind the surround to the framing
16. What is the minimum negative pressure differential typically maintained in a mold remediation containment relative to adjacent areas? → -0.02 inches water column (WC)
17. During mold remediation of a commercial kitchen, which additional hazard must the remediator consider that differs from typical residential jobs? → Presence of food-borne pathogens combined with mold in grease-laden environments
18. What moisture condition must be achieved in building materials before post-remediation verification clearance should be granted? → Materials must be at or below 16% moisture content for wood
19. When using hand scrubbing to remove surface mold, the scrub brush should be: → Bagged and discarded or decontaminated after use
20. Which mycotoxin produced by Aspergillus flavus is classified as a Group 1 human carcinogen? → Aflatoxin B1
21. What is the primary purpose of a 'critical barrier' placed over doorways during mold remediation? → To prevent spore migration between the remediation zone and adjacent unaffected areas
22. Which standard of practice is MOST important for ensuring quality in Building Materials & Mold Growth? → Following evidence-based protocols while adapting to specific circumstances
23. What information must be included in a written respiratory protection program for mold remediation workers? → Procedures for respirator selection, medical evaluation, fit testing, use, and maintenance
24. A remediator encounters mold on the underside of a roof deck in a well-ventilated attic. What is the MOST probable moisture source? → Air sealing failures allowing humid interior air to enter the attic
25. Under IICRC S520 guidelines, what is the minimum safe distance that unprotected building occupants must maintain from a Level II remediation area? → The adjacent room must be vacated
26. After completing mold remediation, what is the purpose of a post-remediation verification (PRV) inspection? → To confirm the work area is dry, visually clean, and free of mold odor before clearance
27. What does a musty odor in a building without visible mold most likely indicate? → Mold may be hidden inside walls, under flooring, or in HVAC systems
28. A moisture reading of 18–28% WME (wood moisture equivalent) on a drywall scan using a non-invasive meter most likely indicates: → Elevated moisture that suggests possible wetting of the wall assembly
29. What is the primary function of melanin pigment in mold cell walls? → Protection against UV radiation and desiccation
30. Stachybotrys chartarum is classified as a 'hydrophilic' mold, meaning it requires: → Water activity above 0.93