- Although the flame will usually burn out very quickly and dissipate little radiant heat, hydrogen ignites over a wide range of concentrations (from 4 to 74.2 percent).
- A potential explosion hazard exists from reignition if a hydrogen fire is put out without shutting off the hydrogen source.
- Hydrogen becomes explosively dangerous if it accumulates in the upper spaces of a structure.
- In bright ambient light, the pale blue flames are invisible to the naked eye. People have been burned by hydrogen fires before they were even aware they had walked into an open flame.
- It takes relatively little heat energy to ignite hydrogen. For example, when hydrogen is released from a pressurized container, rapid gaseous expansion causes an increase in temperature due to its negative Joule-Thompson coefficient and the heat thus generated may cause spontaneous ignition.
- Hydrogen is easier to detonate if it is in a confined space, such as a tunnel, garage or the interior of a car. Care must be taken to eliminate sources of ignition, such as sparks from electrical equipment or static electricity, open flames, and extremely hot objects.
Until there are suitable answers to these questions, automotive fuel cells are, and will remain, interesting laboratory experiments. As a service to your readers, BusinessWeek's editorial evaluation should reflect this reality.
- There are safety and environmental questions that need to be resolved before we embrace the hydrogen economy.
- In order for hydrogen to become an attractive carrier of energy, we must develop a far less energy intensive manufacturing process.
- No one has developed a reliable, practical and affordable fuel cell and unless someone has been able to change the laws of physics, burning hydrogen as a motor fuel is improvident.