Headscratchers / Batman: Arkham Series

• How does the explosive gel not blow up inside of the can when Batman presses the button?
  • It could undergo a chemical change when it exits the sprayer (perhaps reacting to oxygen) that makes it explosive while the rest in the can would be inert
    • This makes sense since after the gel is sprayed, it actually swells and grows slightly as if expanding into shape

• Why doesn't Batman ever add something in his costume so that he would get a warning in case of the air he is breathing is toxic? For the first chronological game, it is plausible but after that, it is a wonder why it's never mentioned he is not using a detector or adding something to his mask for it
  • It's Gotham City. Chances are 85% of the air is toxic fumes from pollution alone, never mind even basic 'toxins' like cigarette smoke, bleach fumes, etc