RMS Cheat Sheet 2026

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

1. What is the minimum number of post-mitigation radon tests required before issuing a compliance certificate under most state programs? → One short-term or long-term test
2. What are the key health concerns associated with radon exposure? → Increased risk of lung cancer
3. What is the recommended placement for a post-mitigation radon test device? → Lowest livable area, at least 20 inches above the floor
4. What is a sub-slab depressurization system? → A system that vents radon from beneath the building using pipes
5. Which pipe diameter is most commonly specified for radon mitigation suction pipes in residential installations? → 4-inch PVC
6. In building science, 'air barrier continuity' is important for radon control because gaps in the air barrier: → Allow pressure-driven soil gas to bypass intended entry resistance points
7. What is the purpose of sealing slab penetrations and expansion joints in a commercial mitigation project? → To reduce radon entry pathways and improve system efficiency
8. The ANSI/AARST standard for mitigation in multifamily housing is designated as: → ANSI/AARST MAMF
9. Which diagnostic tool is used to measure the pressure differential between the basement air and the sub-slab soil to assess radon entry potential? → Manometer or digital pressure gauge
10. When working in a confined space during radon mitigation, what OSHA standard primarily governs entry procedures? → 29 CFR 1910.146 (Permit-Required Confined Spaces)
11. What does Working Level Month (WLM) measure? → Cumulative radon progeny exposure over time (1 WLM = 1 WL for 170 hours)
12. Which type of test device is considered the gold standard for post-mitigation confirmation testing? → Long-term alpha track detector (ATD)
13. Which document is required before beginning radon mitigation work in a commercial building in most U.S. jurisdictions? → A building permit
14. A building has both a basement and a crawl space. What mitigation approach typically provides the most comprehensive radon reduction? → Install separate mitigation systems for each area
15. What role does sub-slab ventilation play in radon mitigation? → It helps vent radon from beneath the foundation
16. When should a radon contractor perform a post-mitigation test? → At least 24 hours after system activation, following EPA/state protocols
17. Which type of radon test device is considered a 'passive' measurement device? → Electret ion chamber
18. According to ANSI/AARST standards, what is the maximum allowable post-mitigation radon level that defines a successful mitigation? → 2 pCi/L
19. A home tests at 3.8 pCi/L on an initial short-term test. According to EPA guidance, what is the recommended next step? → Conduct a follow-up test to confirm the result before deciding on mitigation
20. What is the primary advantage of using a long-term radon test (90+ days) over a short-term test? → Better representation of annual average radon exposure
21. During post-mitigation testing, closed-house conditions are required for at least how long prior to and during the test? → 24 hours
22. When radon decays inside the lung, its progeny deposit alpha energy predominantly in which cell layer? → Basal cells and secretory cells of the bronchial epithelium
23. What is the purpose of a U-tube manometer in a radon mitigation system? → To indicate fan operating pressure differential
24. Which type of radon testing device provides immediate results? → Active radon detectors
25. The EPA classifies radon as a Group A carcinogen because it is: → Known to cause cancer in humans based on sufficient evidence
26. What is the primary purpose of performing diagnostic testing before installing a radon mitigation system? → To determine optimal sub-slab communication and suction point locations
27. If a mitigation system test pipe shows no pressure differential when the fan is running, what should be checked first? → Whether the suction pit properly connects to the sub-slab environment
28. An RMS professional must ensure that a radon mitigation system does not create which hazardous condition in the building? → Backdrafting of combustion appliances
29. What is the recommended safety measure when working with radon mitigation systems in confined spaces? → Proper ventilation and monitoring are crucial
30. What is the purpose of a U-tube manometer installed as part of a radon mitigation system? → Indicate whether the fan is creating negative pressure in the suction pipe