Steve, The situation I am thinking of is where you have a complete power outage. The lathe will take awhile to coast down (especially since the motor will not brake the way it does under power - if I understand it correctly). The vacuum pump will quit running. Since air is compressible, it should take a (very) slight amount of time for the suction to go out of the lines and tubing as air leaks into the system. If I lose power in my basement shop (which is, thankfully, rare) I have some emergency lights, but but they are dim enough, I think I would lose vision for maybe a half second. Based on Dave's experience, with the addition of a 5 gal tank, I would have a second or two to gather my wits and drop to the floor (take cover behind the toolrest/lathe bed) before the project got launched! Does that make sense? The likelihood is low, but for $25, it seems like a worthwhile addition.