What are HHO generators?
HHO generators are only readily available through specialist mail order websites for self-assembly in vehicles including suppliers whose products range from apparently comprehensive kit to components bought from a DIY or hardware store including glass or plastic jars and plastic or rubber tubes with unsecured push fit connections. In 2011, former BSS Examiner Graham Freeman, provided an informative information sheet on this subject.
How HHO are reported to work.
The devices turn water into a mixed gas of hydrogen and oxygen when water molecules are stimulated by an electrical current, with the water separating into its constituent parts, hydrogen and oxygen.
The mixed gas 'generated', sometimes called HHO, oxyhydrogen, hydroxy or Brown's gas, is diverted off and fed into the fuel/air delivery system of the boat's engine where it augments the normal fuel being used in the combustion process.
The hydrogen is delivered into the engine fuel system by using the vacuum generated during the combustion cycle, thus it does not need any pumps or other external devices to move the hydrogen into the fuel/air combustion process.
Using an HHO generator is claimed to save fuel and reduce emissions, however counterclaims say that the devices reduce, rather than improve fuel efficiency.
What are the potential risks?
General risk issues - Should a jar crack or tube dislodge or fracture when the HHO is active then the potential is for a leak of oxyhydrogen in the engine space to be ignited by the multiple sources of ignition within that space. Oxyhydrogen fires or explosions can be anticipated where the concentration is higher than 4% in air.
The concern is heightened by the infancy of the technology and the lack of controls over the manufacture and installation of HHO generator products and components in a marine environment.
There is also a lack of sure knowledge as to the effect of HHO generators on engine life.
In summary the nature of the risk to boaters, other waterway users and Navigation Authority staff is the same as with any other risk of ignition of explosive mixes of vapour and air.
The fact that there are no known accidents or incidents, and the estimate of small numbers of such devices on boats, indicate that the likelihood of an incident is very low overall. However concerning those boats fitted with such devices the likelihood of an incident is high, due to the nature of the gas generated, the multiple ignition sources in engine spaces and the developmental stage of the product.
The severity of any incident involving an ignition of oxyhydrogen in a boat's engine space is likely to involve life-threatening injury and damage.
Although the overall likelihood of an incident involving the escape of hydrogen from an HHO is low (especially in view of the estimated small numbers of such devices on boats), the likelihood of an incident involving one of the total number of boats fitted with such devices is high;
Examiner risk issues - because the oxyhydrogen gas is only generated when the unit is switched on or connected to the battery source and the main engine running it is recognised that risk to examiners is very low time of a BSS examination, however there is a small risk that escaped gas may have formed in trapped pockets.
Some of the devices available use aqueous solutions instead of water and this may include potassium hydroxide. Potassium hydroxide presents a hazard to human health if it comes into physical contact with skin or eyes.