The mask should stop some of the evaporation process once MrLapLap is unconscious, the idea is that he will become self basting . He’ll be passed out completely on both these flights. The mask would have to be lined with salt encrusted nails for him not to be able to sleep in it!
Turns out that it isn’t that different to the FFP2 (and sometimes FFP3) masks he already uses as he often has to work within clouds of fine dust (like the stuff MDF/fibre boards give off when you cut them). He’s had training on fitting these and is used to wearing them.
Anyway, job done, we’ll see what the advice is next week (not that he would have any opportunity to get anything then, it’s now or never.)