The method
Before using the result
- Use dry-air mass flow, not moist-air volume flow. Signed rate comes from measured states and is not a rated daily dehumidifier capacity.
Worked examples
These original training examples illustrate the method for IICRC Applied Structural Drying Technician (ASD). Use the matching “Load example” button above to explore a variation; example values are not equipment settings or prescribed criteria.
1. Worked example
Convert a measured humidity-ratio change and dry-air mass flow into water removal. Keep this short-term stream balance separate from advertised equipment capacity.
- Inlet humidity ratio (g/kg dry air)
- 15
- Outlet humidity ratio (g/kg dry air)
- 8
- Dry-air mass flow (kg/s)
- 0.5
- ΔW = (15 − 8) / 1000 kg/kg.
- Removal = 0.5 × ΔW = 0.0035 kg/s.
- Water removal rate: 12.6 kg/h
- Constant-rate equivalent: 302.4 kg/day
2. Comparison example
Compare a different supplied condition using the same method. For Restoration Cert Lab, the important check is that the input meaning, units and method assumptions still match the problem.
- Inlet humidity ratio (g/kg dry air)
- 15
- Outlet humidity ratio (g/kg dry air)
- 10
- Dry-air mass flow (kg/s)
- 0.5
- ΔW = (15 − 10) / 1000 kg/kg.
- Removal = 0.5 × ΔW = 0.0025 kg/s.
- Water removal rate: 9 kg/h
- Constant-rate equivalent: 216 kg/day
Check your understanding
1. Which relationship is used?
Water removal = dry-air mass flow × (Win − Wout), using kg/kg humidity ratios.
2. Which assumption should you check first?
Use dry-air mass flow, not moist-air volume flow. Signed rate comes from measured states and is not a rated daily dehumidifier capacity.
3. How should you verify a different unit system?
Convert every input to the displayed calculation units first. Equivalent physical inputs must give equivalent results; a unit label alone does not convert a number.
Continue with the matching exam topic
This tool connects to IICRC Applied Structural Drying Technician (ASD) free practice. Work through a question independently, then use the calculation steps to identify where your method differs. The tool stays free whether or not you choose paid preparation.