Use distilled water over tap water. Tap water generally has iron and calcium mineral deposits (hard water). When used in a vaporizer, tap water may leave behind scaling, crusting and white dust deposits. According to Drugs.com, mineral deposits can encourage bacterial and fungal growth. Mineral deposits, long term, will also affect the optimal function of your vaporizer.
Change the vaporizer water daily. Wipe dry all external surfaces, especially the electrical cord, and only fill the vaporizer to suggested levels. Vaporizers don't require filters which can breed mold, but mineral deposits and dirt can accumulate in the reservoir. Clean the entire unit every third day. With a brush, clean any accumulated scaling or mineral deposits. As a precaution, wipe surfaces with a 3 percent hydrogen peroxide solution. Rinse well before you fill the unit with fresh distilled water.
Steam vaporizers heat water to boiling with an electrode or heating element. The hot steam released, at 170 degrees F, can cause scalding and burns. Some vaporizer models have vapor cooling attachments, but as a precaution, manufacturers recommend that vaporizers be installed away from children and pets.
Vaporizers are meant for short-term use and should never be plugged in when you're away and when water levels drop below recommended levels. If water levels fall below the heating element, it's considered "standing water." According to the Asthma Society of Canada, standing water is a breeding ground for mold and bacteria. Conversely, if room humidity is too high, over 45 percent, mold and mildew can grow. If you plan to use a vaporizer often, purchase a portable hygrometer, which measures air humidity. Ideal humidity is 30 to 35 percent.