Factual error: Though extremely modest on today's standards, the dress worn by Clara to the hoedown shows far too much cleavage for the time. No schoolteacher would ever wear a dress like that in the 1880s.
Factual error: Asystole (the lack of cardiac activity, also known as the 'flatline') is not treated with defibrillation (electric shocks) but with alternating doses of the drugs epinephrine and atropine.
Factual error: Throughout the entire film Burt holds all of his rifles' butts underneath his armpit, rather than against his shoulder. A trained "survivalist" such as him would surely know better. Holding the "elephant gun" in such a way would most likely break his arm, wrist and hand when it fired. (00:58:20)
Factual error: When the Security Guard in the pump room gets bitten on the nose, he starts shooting with his revolver (a SIX shooter). Count the bangs. He manages to fire SEVEN times. (00:39:45)
Factual error: During the scene where Peyton is hanging from the helicopter, Durant is firing at him with a grenade-launcher. He hits several cars, most of which end up in flaming wrecks. Despite this, traffic continues as normal... If you saw cars around you exploding, would you casually continue on, oblivious? This error is especially visible with the truck driver, whom reacts to Peyton landing on top of his truck, but seems oblivious to the chaos behind him.
Factual error: The spider being fried by the fuse box simply can't happen. Fuses are insulated for that very reason.
Factual error: Throughout the movie, whenever the domes are breached (which happens much too often) it is said that there is only vacuum outside. But Mars has an atmosphere. Its thin and mostly CO2, but it's there.
Suggested correction: While it is not a true vacuum outside the domes, it's around 1% of Earth's atmosphere. The effect of a dome breach would be close enough to a true vacuum to the people affected.
Suggested correction: "Vacuum" is a colloquial way of saying low pressure, just like the 'vacuum' you use to clean the house creates a low pressure to cause suction.
Suggested correction: It's possible human colonization of the planet affected the atmosphere.
If the Martian atmosphere ceased to exist, the sky would be always black, never red as seen in the movie (Mars' sky is actually a butterscotch color during daytime and bluish during twilight).
Factual error: April interviews (live) the police Chief and then tries to take the train back home. The subway station shows that it's the City Hall stop, and she just finished her interview with the guy, which happened mid-afternoon as you can see by the clock in the corridor. Despite being New York in the middle of the day, there's not a soul in the station, nobody got off the train she just missed, nobody around at all on any of the multiple platforms. It's a trope good for a scene set at 3 AM, not 5 PM. (00:19:25)