[Robert]

FWIW I do my overnight YOS (yeast oxygen scavenging) at room temperature and it seems to work fine. 

Reading your procedure of overnight YOS, I was wondering if I did my "YOS" the evening before in the water jugs that I store my Mash and Sparge water, then pour that water from the jugs into the MT and the HLT on the morning of brewday, then heating the water to the required temperature, would the yeast keep working after the splashing/pouring of the water into the two vessels? Or would there be oxygen take-up and defeat what I thought I was preventing.

Thanks

tom

I think the splashing would defeat the purpose.   I treat my water in my MT and HLT, add the yeast and cap the vessels (floating caps to eliminate any exposed surface area.)  There's good evidence that even uncovered, the yeast can hold the water below 0.2 ppm DO overnight, because they can scavenge faster than the rate of simple diffusion from the atmosphere.   But that kind of splashing can be an effective way of aerating wort for pitching, so I'm sure it would leave you back at square one.   

[millstone]

Thanks Robert very helpful, I'll try the YOS the morning of brewday, as you have said, "Yeast scavenge oxygen extremely rapidly, and should be most active right before the heat kills them"

Tom