Horizon Fuel Cell Technologies H-500XP, User Manual

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1.5 Flammability and Volatility
Hydrogen is flammable over concentrations of 4 – 75% by volume in air, and is
explosive over concentrations of 15 – 59%. As a result, even small leaks of
hydrogen have the potential to burn or explode. Leaked hydrogen can
concentrate in an enclosed environment, thereby increasing the risk of
combustion and explosion.
Hydrogen flames are pale blue and are almost invisible in daylight due to the
absence of soot. Due to its high buoyancy and diffusivity, burning hydrogen rises
unlike gasoline, which spreads laterally.
A flammable or explosive hydrogen mixture is easily ignited by a spark or even a
hot surface. The auto-ignition temperature of hydrogen is 500 °C (932 °F). The
energy of a hydrogen gas explosion is 2.4 times that of gasoline or methane for an
equal volume. Hydrogen gas explosions are therefore more destructive and carry
further.
WARNING!
A mixture of hydrogen and air is potentially flammable and
explosive and can be ignited by a spark or a hot surface.
As in the presence of any fuel, all sources of ignition, including smoking, are not
permitted in the vicinity of the system.
WARNING!
Keep all sources of ignition away. Smoking is not permitted in the
vicinity of the H-500XP.
1.6 Oxygen Depletion
Oxygen is a colorless, odorless, non-toxic and tasteless gas. Oxygen is essential
for life in appropriate concentrations.
Ambient air contains up to 21% oxygen. Oxygen levels below 19.5% are
biologically inactive and may act as simple asphyxiates. Effects of oxygen
deficiency may include: rapid breathing, diminished mental alertness, impaired
muscular coordination, faulty judgment, depression of all sensations, emotional
instability, and fatigue. As asphyxiation progresses, nausea, vomiting, prostration,
and loss of consciousness may result, eventually leading to convulsions, coma,
and death. At concentrations below 12%, immediate unconsciousness may occur
with no prior warning symptoms.