>>77005672He froze the sensors, which kept the alarm from going off. Basically they got so cold they couldn't send the electrical signal necessary to trigger the alarm. Not that far fetched, extreme temperatures fuck with electronics in some pretty serious ways.
Now as for the lasers being frozen, that might be more a case of a peculiar property of water. See water goes from one extreme to another more quickly than it does from a "moderate" state to an extreme one. For example, when it's freezing cold outside throw a pot full of lukewarm water out into the snow and you'll find that liquid water hits the ground. Now try that same experiment with boiling water, and you should find a powdery mist of newly formed snow hits the ground instead.
If the lasers in the show were able to heat the air immediately around them slightly more than the ambient air, it is possible that a rapid drop to insanely low temperatures could cause ice crystals to form around the lasers, but not in the rest of the air. It would be a stretch, but more of a basis in physics than 90% of Flash bullshit science.
So to answer the OP, freezing the lasers is more ridiculous. Breaking the sensors with cold so that crossing the beams doesn't set off the alarm is somewhat sensible.
