Hi Everyone

The following edited exchange of emails indicates a problem with heat exchangers that may be unknown to expeditioners & is circulated with a view to saving lives. Had there been only 2 of us involved we would not be here now and there will be pots in circulation that have no warnings.


Hi Guys,

You might like to feedback a little information re the functioning of your heat exchanger pots, based on my rather unpleasant experience in Mongolia.

The pot functioned well at 2400m & at 3100m but at 3600m I experienced problems with CO poisoning. In fact I had stopped breathing & my tentmate was fitting when the others dragged us out. Apparently it took some time to get me breathing on my own again.
We were cooking inside the inner tent but with vents open for ventilation in exactly the same way as I have done for many years now. The only change in the system was the new pot. Having tried to find out what went wrong I have reached the following conclusions based on occasions on which there was a noticeable increase in fumes from the stove & decrease in flame intensity despite a verifiable full canister of propane/butane fuel:
When melting snow there is always a danger of cooling the pot to the point where there is substantial condensation on the bottom so that the stove wastes energy evaporating the condensation (& consequently to some extent cooling the pot - cf a fridge). With normal pots that can be short-cut by wiping the bottom with a sponge but with the heat converter that is difficult enough to deter any attempt to do so. The heat converter also inhibits the evaporation of the condensation trapping it within the burner area & therefore reducing the amount of oxygen available to the burner. Every time there was evidence of condensation evaporation the flame struggled & we experienced some symptoms of CO effects.

I would stress that being aware of this problem enabled us to take measures that overcame it, principally by managing the snow melt so that the pot was not cooled to the point where condensation occurred. I have encountered many people in the course of the expeditions that I have led who were unaware of the condensation issue re any stove, but particularly with snow melting, so would suspect that others would have more difficulty than me in working out what was going wrong (in my case largely with hindsight experiments after nearly dying!). It is also worth noting that this is a very specific problem related to the functioning of the pots at altitude when oxygen is depleted and when melting snow is the water source. The phenomenon was not encountered during our Antarctica expedition or at lower altitudes in Mongolia but that unfortunately tends to reinforce one's confidence in the system and blinded me to the fact that the burner was not burning properly (I put it down to th!  e gas running out & turned up the burner with the above consequences).

A warning about the problem of condensation restricting oxygen supply at altitude included with the instructions for the stove could well be all that is needed to save a life.

Regards,
Dave

Dear Dave,
It was quite shocking to read you incident report above! We have been looking in to it and I want to give you a short feedback on our findings and actions.

Your MSR Superfly has pot supports that do not reach the support ring on the pot which makes the burner come “inside” the heat exchanger. Further, the burner has 45 degree angled flame and this combination makes the stove direct the flames on to the heat exchanger. This results in high CO emissions as the flame gets quenched before full combustion has taken place. Most likely this problem is further enhanced at high altitudes where the lack of oxygen can make CO emissions even higher.

We have decided to print warning symbols on the pots from now on.

Regards,
Dave Wynne-Jones