A solution of boric acid dissolved in hydrogen peroxide is helpful for killing mold and fungus, as well as to combat mineral deposits left from hard water. Though the solution kills mold, a single application does not necessarily get absorbed deep enough to kill it all. Therefore, a layered approach of repeated moistening and scrubbing is needed.
Combine a half-gallon of 10% hydrogen peroxide (H2O2) with a cup of boric acid. Cut the proportions if you think you'll use less in a four-hour period, because H2O2 degrades and loses its antiseptic quality when exposed to light. If you don't have 10% solution, cut 35% solution (which is more commercially available, called "technical-grade") with 3 parts water. Don't use the H2O2 from the drug store, which is a mere 3%.
Moisten the mold thoroughly with the solution before scrubbing. Scrubbing dry mold can send it airborne, spreading it to other parts of the room. Use a face mask.
Scrub the moistened mold. Then wet the layer below. Then scrub it. Continue until the mold is gone. Take a break if the mold is getting to you, but keep in mind that the H2O2 degrades and won't be effective at killing the mold after four hours of light exposure. Never scrub mold that has not been thoroughly moistened.
Apply the H2O2-boric acid solution to teapots, coffeemakers and humidifiers to get rid of hard-water mineral buildup. Let it sit for several hours to get through all the layers of minerals.
After the mold is removed, consider installing both a dehumidifier and a fluorescent light to run a few hours a day. The former prevents the moisture that mold likes; the latter gives off UV rays that kill mold.