Yes, Safeflame unit will not get flashback from their flame and torch. It is not magic. Safeflame was the result of an EU funded project to research for a "safer flame" without using compressed gas bottles, chemicals and/or alcohols.
Traditionally all flames from Propane, Acetylene, Natural Gas, HHO fuel gases are "pre-mix" flames ie the Fuel gas is mixed with oxygen before it reaches the torch tip for combustion. These flames are very prone to "Lightback" or "Flashback". Too much gas, the flame will try to lift off, too little gas the flame will try to travel in the opposite direction into the torch.
Flashback can and will occur because it is a "pre-mix" gas system. Hence for those applications there is a requirement to install flashback arrestors (Fba) in the gas hoses / torches for safety reasons.
These Fba's have to be certified for the appropriate fuel gases. There will be Fba for propane, acetylene, hydrogen etc. We are not aware of any Fba's that are certified for HHO fuel gas over 0.5 bar that is available in the market and therefore care should be taken to ensure that the correct certified Fba's are used by whatever system that you choose to use.
Some of those HHO suppliers are claiming that they use Fba's that are tested to safety standards, in particular ISO 5175 and EN 730. However these standards specifically excludes Oxy-Hydrogen systems or HHO. That is a blatant mis-representation of facts. The responsibilty for the use of those machines to make sure they are safe and "fit for purpose" lies with you. So care should be taken in choosing your "Gas from water system".
Stoichiometric HHO gas mixture is the worst mixture for flashback to occur. For a lot of HHO systems in the market today, they use a few Flashback arrestors in series to try to overcome this problem .
For Safeflame unit with the specially designed "post-mix" torch (i.e the gases are only mixed at the tip of the torch), Fba is not necessary and flashback is not possible. Why ? Because the fuel gas, hydrogen is only mixed with oxygen at the tip of the torch nozzle and on the outside. When there is too little gas or too large a torch nozzle tip, the flame will try to travel back to the inside of the torch. It will not produce a flashback because when the flame tries to go back into the hydrogen gas line which has 100% pure hydrogen, it won't combust. If the flame tries to go back into the 100% pure oxygen gas line, it will be the same because oxygen on it's own won't combust. Hence Flashback is not possible.
Another side benefit of the "post-mix" torch is that the torch nozzle is very tolerant and frequent change of nozzle tip to match the flame size is not necessary. Of course if the post-mix gas is too much it will eventually lift off but usually at reasonably high gas output. Hydrogen is a very diffusable gas and so is the perfect gas for post-mix flame.