PHB pg 278:
ONGOING DAMAGE
✦ Start of Your Turn: You take the specified damage at the start of your turn. Example: If you’re taking ongoing 5 fire damage, you take 5 points of fire damage at the start of your turn.
✦ Saving Throw: Each round at the end of your turn, make a saving throw (page 279) against ongoing damage. If you succeed, you stop taking the ongoing damage.
✦ Different Types of Ongoing Damage: If effects deal ongoing damage of different types, you take damage from each effect every round. You make a separate saving throw against each damage type.
✦ The Same Type of Ongoing Damage: If effects deal ongoing damage of the same type, or if the damage has no type, only the higher number applies.
Example: You’re taking ongoing 5 damage (no type) when a power causes you to take ongoing 10 damage. You’re now taking ongoing 10 damage, not 15.
So, if You had cont. dmg from a torch, and then got shoved into a bonfire, the torch would be effectively negated.
Hope this helps!