Several good papers and reports have been written concerning safety in the use of hydrogen. Hydrogen is a very high energy fuel and it therefore must be treated with caution and respect. Hydrogen is colorless and odorless and is therefore not detectable by human senses. The higher ignition temperature of hydrogen may be considered a plus. Hydrogen gas can cause suffocation by exclusion of oxygen but it is not toxic. The low energy required for ignition of hydrogen, its wide limits of flammability, high volatility, and high flame velocity would seem at first thought to make hydrogen a very hazardous fuel. The wide combustibility and detonability ranges for hydrogen are usually cited as cause to rate the fuel as especially hazardous. The hydrogen pool fire will last only 15 s. However, smoking must be banned in areas where hydrogen is being handled because the flame from a match or cigarette lighter will ignite a hydrogen-air mixture.