I guess then, that we need rules that do not encourage such House Rulings - House Rulings that were almost universal in one DM after another's games I was in for years.
There was a lot of misunderstanding about oil in 1E. Eager players leaped on the vagarities of the situation to use fire as a Superweapon at low levels, while flummoxed amateur DMs watched their scenarios get fried.
Your posts make me think that very specific descriptions are needed concerning fire attacks, and fire spells.
For example, just exactly *how* long does a fireball stay in existence? Exactly how hot is it? (just say it will melt lead, as the 1E rules stated, is too vague.)
If oil 'splashes' a target for 1d3 points of damage (ala 1E), does that 'splash' mean the target is now partly covered in flames (save for items, make a full round action to put out the flames), or merely singed (no fire on the target at all) or something in between?
If a target is aflame (as per, engulfed in flames, movie-style) can that target take any action at all? Can the target take an action with a successful saving throw (against the pain.) Can the target take any action it pleases?
Just how much does the pain of being burned affect the target? For example, we know that if a wizard takes 3 points of fire damage, he must make a DC check against that damage to successfully cast a spell. In 4E, will he need to do this? Will anyone else need to do this?
If a target is only partially on fire (such as, his boot is on fire) and he takes no action to put it out, does that mean the fire spreads to the rest of his clothing? (fire does like to spread ...) Or does it go out (boot didn't want to burn ...) Or what?
I mean: When all is said and done, fire is a popular weapon (the effects of that weapon are ghastly, obviously.) Characters are going to play with fire. So fine. Let's have some exact definitions of how fire works in combat situations.
And smoke, too. If the whole dungeon corridor is smoked up until you can't see your hand in front of your face, that should have some effects. Partial Cover? Full Cover? Invisibility? Or how about simply checking Direction Sense so you don't blunder right into that wall, and knock yourself down?