On 24/02/17 13:22, newshound wrote:
On 2/24/2017 12:38 PM, Chris Hogg wrote:

You're suggesting the flame would strike back through the bleed valve
into the radiator? Very unlikely I would think. The mass of cold metal
would quench the flame to below its ignition point, in much the same
way as the gauze in a Davy lamp used by coal miners does.

I wondered that too, but do you feel lucky? Hydrogen is infamous for its
very wide explosive range compared to methane.

Then just open the valve slightly and put a spot of diluted washing-up
liquid on the bleed point. Wait until a small bubble has formed, detach
it, and see what happens when you hold a flame to it.

--

Jeff