| Constant | Description | 
| STEAMINJECTION | Water vapor is added into the airstream through direct steam injection. | 
| ADIABATICAIRWASHER | Water vapor is added into the airstream through adiabatic evaporation using an air washing element. | 
| ADIABATICPAN | Water vapor is added into the airstream through adiabatic evaporation using a pan. | 
| ADIABATICWETTEDELEMENT | Water vapor is added into the airstream through adiabatic evaporation using a wetted element. | 
| ADIABATICATOMIZING | Water vapor is added into the airstream through adiabatic evaporation using an atomizing element. | 
| ADIABATICULTRASONIC | Water vapor is added into the airstream through adiabatic evaporation using an ultrasonic element. | 
| ADIABATICRIGIDMEDIA | Water vapor is added into the airstream through adiabatic evaporation using a rigid media. | 
| ADIABATICCOMPRESSEDAIRNOZZLE | Water vapor is added into the airstream through adiabatic evaporation using a compressed air nozzle. | 
| ASSISTEDELECTRIC | Water vapor is added into the airstream through water heated evaporation using an electric heater. | 
| ASSISTEDNATURALGAS | Water vapor is added into the airstream through water heated evaporation using a natural gas heater. | 
| ASSISTEDPROPANE | Water vapor is added into the airstream through water heated evaporation using a propane heater. | 
| ASSISTEDBUTANE | Water vapor is added into the airstream through water heated evaporation using a butane heater. | 
| ASSISTEDSTEAM | Water vapor is added into the airstream through water heated evaporation using a steam heater. | 
| USERDEFINED | User-defined humidifier type. | 
| NOTDEFINED | Undefined humidifier type. |