What is the role of mass balance in humidification analysis?

• A. To ensure that the moisture and air mass are properly accounted for in the system.
• B. To minimize energy use.
• C. To determine the optimal room temperature setpoint.
• D. To measure outdoor humidity.

Answer: (A)

Mass balance in humidification analysis means treating the moist-air system as a closed-mass system where all sources and sinks of moisture and air are accounted for. You track the rate at which moisture enters the space (incoming supply air with its humidity, any outdoor air brought in by ventilation), the rate at which moisture leaves (exhaust, return air, leaks), and any moisture added or removed inside the space (humidifier output, dehumidification). In steady-state, the moisture entering equals the moisture leaving, so there’s no net storage change. This balance lets you determine how much moisture must be added by the humidifier to achieve the desired humidity, given the ventilation rate and outdoor humidity, or verify that a given humidification rate will maintain the target conditions. It’s about keeping the moisture and air mass properly accounted for, not about minimizing energy, picking a temperature setpoint, or directly measuring outdoor humidity.