With fans turning at top speed, Mike computed it would take four minutes and a bit to reduce oxygen to effective zero—so, five minutes of increasing hypoxia, five minutes of anoxia, then force lower lock while Mike shot in pure oxygen to restore balance. This should not kill anyone—but would knock out a person as thoroughly as anesthesia. Hazard to attackers would come from some or all of those inside having p-suits. But even that might not matter; hypoxia is sneaky, you can pass out without realizing you are short on oxygen. Is new chum’s favorite fatal mistake.