CPR CPR Equipment Selection & Deployment 1 — Questions and Answers
Question 1: Which class of dehumidifier is most commonly deployed for structural drying in residential water damage jobs?
- Desiccant dehumidifier
- Refrigerant (mechanical) dehumidifier (Correct answer)
- Enthalpy dehumidifier
- Evaporative cooler
Correct answer: Refrigerant (mechanical) dehumidifier
Refrigerant dehumidifiers are the industry standard for residential drying due to their high efficiency at typical indoor temperatures and lower operating cost.
Question 2: Under what ambient temperature condition does a desiccant dehumidifier outperform a refrigerant unit?
- Above 80°F and high humidity
- Below 45°F where refrigerant coils lose efficiency (Correct answer)
- At exactly 70°F with 50% RH
- Only in outdoor environments above freezing
Correct answer: Below 45°F where refrigerant coils lose efficiency
Refrigerant dehumidifiers lose significant capacity below ~45°F because the evaporator coils frost; desiccant units use chemical adsorption and operate efficiently in cold conditions.
Question 3: The primary purpose of axial air movers in structural drying is to:
- Filter airborne mold spores
- Create high-velocity airflow across wet surfaces to accelerate evaporation (Correct answer)
- Measure airflow in CFM across drying zones
- Compress air into wall cavities for rapid drying
Correct answer: Create high-velocity airflow across wet surfaces to accelerate evaporation
Axial air movers direct high-velocity air across wet floors and walls, thinning the boundary layer of humid air at the surface and accelerating moisture evaporation.
Question 4: According to IICRC S500 guidelines, what is the standard placement ratio of air movers to dehumidifiers for a typical residential water loss?
- 1 air mover per 1 dehumidifier
- Approximately 4–6 air movers per dehumidifier (Correct answer)
- 10 air movers per dehumidifier
- Dehumidifiers are used without air movers in residential settings
Correct answer: Approximately 4–6 air movers per dehumidifier
IICRC S500 drying science calls for roughly 4–6 air movers per dehumidifier so that evaporative capacity is matched by sufficient moisture removal capacity.
Question 5: A restorer is drying a Category 2 loss in a room with 200 sq ft of affected flooring. Using the 1 air mover per 50 sq ft rule of thumb, how many air movers should be deployed?
- 2
- 4 (Correct answer)
- 6
- 8
Correct answer: 4
200 sq ft ÷ 50 sq ft per air mover = 4 air movers as the initial equipment placement estimate per IICRC S500 guidance.
Question 6: Which type of air mover is preferred for drying wall cavities using the injection-drying technique?
- Large industrial axial fan
- Centrifugal (snail-shell) air mover with hose attachment port (Correct answer)
- Box fan on a stand
- Whole-house HVAC fan set to 'on'
Correct answer: Centrifugal (snail-shell) air mover with hose attachment port
Centrifugal air movers generate higher static pressure than axial units, enabling air delivery through hoses inserted into wall cavities for directed injection drying.
CPR CPR Equipment Selection & Deployment 1
Which class of dehumidifier is most commonly deployed for structural drying in residential water damage jobs?