My take on the accuracy and plausibility of MacGyver Season 1 Episode 7: Can Opener aired November 4, 2016 on a scale of (Accurate, Probable, Possible, Unlikely, Bogus).
If there are any other statements or events you would like me to analyze, please add a comment with a brief description and the time in the show.
1:48 Gas truck, Fire hose, and cable lock to create a ring of fire
Unlikely (guess): It's not clear why the gas truck has a nozzle on top. It is unlikely that the cable lock would create a tight enough seal. I think it is unlikely that a bullet would provide enough heat to ignite the gasoline.
10:19 Riley: "They ran a security update and patched the hole in their system I was using as a back door."
Accurate: Calling it a "Back Door" might not be 100% accurate; however having a reliable exploit for a known vulnerability would be just as good.
12:20 An inhaler won't spray, because the pin in the cartridge is missing.
Possible: While using a piece of a fork to temporarily replace the pin could work, it would probably not be that reliable. Additionally, the problem is with the cartridge and not the inhaler, so inserting a new cartridge would have fixed the problem.
17:02 Jack: "'Jail', what an idiot. I just bypassed his password.
Riley: "It was in sleep mode Jack. You literally could have hit any key."
Bogus: Jack hit 9 keys to type 'jail'. Then the screensaver (not sleep mode) turned off when Jack pressed <enter>. It should have turned off when the first key was pressed.
19:58 Mac: "A towel soaked in water can pack a pretty good punch. Add some powered bleach to give it a little bit of a sting. Wrap the whole thing in a sheet for extra range, and you have yourself a weapon from the middle ages called a flail."
Possible (guess): While the towel soaked in water is not an insignificant amount of mass, I doubt it would be hard enough to reliably incapacitate an attacker.
26:42 Hydrogen electrolysis
Unlikely (guess): Mac uses a radio battery, salt from food, and water to create hydrogen. It's hard to tell if the battery contains enough power to produce enough hydrogen and I have no idea how much hydrogen would be necessary to blow the steel door out. I highly doubt they could survive the pressure necessary to blow out the door. Using the wires from the light fixture to ignite the hydrogen appears realistic. He only undoes a wire nut, so he could be fairly confident of not shocking himself.
31:00 Ladder from shelves
Unlikely: Mac's paperclip screwdriver would not be stiff enough to unscrew most shelve. Most shelves use the shelves as the horizontal supports, so it is not possible to use one end as a ladder once the shelves have been removed.
31:53 Chemical embrittlement
Bogus: Fire extinguisher (CO2), Alcohol to create a very cold liquid to embrittle steel bars. Mac does not put enough of his mixture on the bars to possibly do anything.
35:57 Manually flashing a car's taillight
Accurate: Auto electrical systems run on 12V so Mac can safely touch the wires with his bare hands.
37:50 Torture using Nitrogen
Bogus: According to Wikipedia, inert gas asphyxiation does not cause pain, since pain comes from high CO2 levels.
39:08 Pressure vessel rocket
Bogus: Somehow Mac is able to magically kick the valve off of a nitrogen tank, turning it into a projectile that perfectly takes out the bad guys.