Before You Install a Steam Humidifier, Test Water Conductivity! Installing a steam humidifier can be one of the most effective ways of increasing the humidity in one’s home; however, selecting the right model requires a little more consideration than other humidifier models! Steam humidifiers utilize electrode steam technology, whereby electric current is passed between electrodes inside a water-filled canister to heat the water within and create steam. This technology relies on water conductivity (provided by the presence of natural minerals in the water) in order to efficiently pass electric current between electrodes. Knowing your water's conductivity is essential in determining which model steam humidifier you should install. If the water does not have ample conductivity, steam humidification may not be the right choice for your home. Testing Water Conductivity: Using the AP-2 Digital Water Tester, test your tap water for electrical conductivity (measured in micro Siemens per centimeter (µs/cm). GENERALAIRE STEAM UNITS: 100 to 500 µs/cm - Requires a Generalaire Low Conductivity (LC) model. 300 to 1,250 µs/cm - Requires a Regular steam model. above 1,250 µs/cm - Installation NOT recommended. APRILAIRE STEAM UNITS: 0 to 125 µs/cm - Installation  NOT recommended. 125  to 840 µs/cm - Use either hard or softened water. 840 to 1,250 µs/cm - Use softened water. above 1,250 µs/cm - Installation NOT recommended. HONEYWELL HM700A1000 STEAM UNIT: 0 to 150 µs/cm - Installation  NOT recommended. above 1,200 µs/cm - Installation NOT recommended.