How do I handle the hydrogen gas safety risk if my hot water system hasn't been used for two weeks?

Before using the dishwasher, turn on all hot water faucets and let the water flow from each for several minutes to release any accumulated hydrogen gas. Hydrogen gas is explosive and flammable, so do not smoke or use an open flame during this time. This precaution applies when the hot water system has not been used for two weeks or more. (Page 2)