How safe is Hydrogen?
What comes to mind when you hear Hydrogen? danger? Do you think Hydrogen bombs? Well, you are not totally alone. Safety has been one of the major public perception challenges facing the rapid adoption of the technology. In an anonymous social media survey that asked two related questions, 49.5% of the respondents believed that Hydrogen is generally safe, while 31,4% regarded Hydrogen as dangerous. Certainly, as progress is scored on improving efficiencies and cost reductions of hydrogen technology, a lot needs to be done to change the perception of the public towards the technology.
Is hydrogen flammable and explosive? Yes. But so are other fuels! In Fact, compared to the most commonly used fuels, hydrogen is safer. For example, Diesel requires a minimum concentration of 0.6% to be flammable while hydrogen has a much higher minimum percentage of 4%. That of gasoline, propane, and ethanol are 1.4%, 1.2%, and 3.3 respectively. Consider the auto-igniting temperature of these gases. In the absence of a flame or spark, Diesel, gasoline, and propane ignite at 210, 260, and 480 degrees centigrade respectively while hydrogen only burns from 580 degrees centigrade.
Again, when gasoline or petrol leaks, they pool close to the ground increasing ignition likelihood, on the contrary, hydrogen disperses rapidly into the atmosphere at an average speed of 20m/s at ambient temperature when it leaks being less dense than air (1/4th density of air). Unlike the case of gasoline and petrol. This does not encourage ignition. In addition, the absence of carbon in Hydrogen fires means they generate low radiant heat and are short-lived.
There could be other potential dangers Hydrogen may pose due to its characteristic nature — odorless, tasteless, has a wide combustion range, and burns with an invisible flame.
Though Hydrogen has a relatively high lower explosive limit (4%) when compared with other fuels earlier mentioned, the range of hydrogen/air mixtures that may propagate a flame is wide: between 4% to 75% hydrogen/air mixtures.
The good news however is that safety systems can be engineered to optimally handle any fail-situation easily. For example, in addition to leak, fire, or heat detection systems, a ventilation system can be built-in to prevent leaks from reaching flammable levels.
From the brief analyses, it is clear that Hydrogen is safe (safer than most commonly used fuels today) if appropriate safety measures are taken. But, is the public aware of this image of Hydrogen. Our familiarity with gasoline insulated us from the fear of its inherent danger.
A lot of work is required to mainstream hydrogen technologies in pursuit of our ambitious climate targets. Overcoming the public perception hurdle will shorten the journey and take us to our destination quicker.
What additional actions do you think could be taken to address the public perception question?