Hey fellow Thought-nauts

I'm about to send my party to Dis, to chase and kill a demon.

While in Hell, should the party receive Fire Damage of Exhaustion over the time they are there?
I was thinking of adding this as a consequence, if they don't prepare and purchase Potions and Rings of Protection against Fire damage.

I have also added Demonleather to the inventory at the shops in Dis, so that they can purchase cloaks that protect from the harsh environments of Dis.

Has anyone done anything similar? How did you structure it?

Thanks in advance

A demon. In hell? I'd leave him where he is. He is already in more than enough trouble. :)

They should just suffer exhaustion- especially the guys in plate armor. Play the demons to their advantages.

Exhaustion is the most appropiate thing I think. Thus, damage would be too much for the party just for being there

As other have said, exhaustion is the way to go. Here are the DMG guidelines for traveling in extreme hot conditions:

When the temperature is at or above 100 degrees Fahrenheit, a creature exposed to the heat and without access to drinkable water must succeed on a Constitution saving throw at the end of each hour or gain one level of exhaustion. The DC is 5 for the first hour and increases by 1 for each additional hour. Creatures wearing medium or heavy armor, or who are clad in heavy clothing, have disadvantage on the saving throw. Creatures with resistance or immunity to fire damage automatically succeed on the saving throw, as do creatures naturally adapted to hot climates.