In fairness, that's not the whole story. When I sauna, I'm not doing anything remotely strenuous. I'm sitting around naked and not feeling the slightest stress. These guys were working in an emergency situation - clothed - and doing physical labor.
Yet it did have that effect. Unless you're claiming the parent is lying? Or are you suggesting it's merely an unlikely event? The fact is people have all kinds of physical issues they might not even be aware of and you can't take that chance with people - not for legal reasons, not for ethical reasons. The best you can do is prepare in advance by training people in the situation to detect if they have any issues with the environment.
