Modeling direct humidifier without HVAC loop in Energyplus

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Hi all. In EnergyPlus, I want to make the humidifier model which operate independently with other HVAC systems. In other words, this humidifier is not included in the HVAC loop, but rather evaporate water to the air directly. However, all humidifier example file in the EnergyPlus, the humidifier increase indoor humidity through the HVAC loop by bringing outside air. Is it possible to model the humidifier to operate alone without HVAC? Thanks.