Let’s look at the verse in question, “For if God spared not the angels that sinned, but cast them down to hell, and delivered them into chains of darkness, to be reserved unto judgment” (2 Peter 2:4).
The word used here for “hell” is “tartaroo” which is a unique word and the only times it’s used in the Bible. I know that some have tried to work it up to mean some type of special location, but it simply means a confinement.
It probably means that the evil angels are confined to planet Earth, and the chains likely indicate that they are limited in what they can do and force upon mankind. There will come a time when they will be loosed from those chains to implement wrath, but it is likely just a reference to their containment here so they can’t roam the universe to lead other worlds astray with their rebellion.
This is not the same as the “hell” known elsewhere in the Bible as “Gehenna” because it is not a place of burning, but of darkness. When “Gehenna” is mentioned there is always fire and burning.
A good reference verse for 2 Peter 2:4 is found in Jude 1:6, “And the angels which kept not their first estate, but left their own habitation, he hath reserved in everlasting chains under darkness unto the judgment of the great day.”
There is no reason to believe that they are facing any sort of punishment in this darkness but are merely kept for their day of judgment, when they certainly will face their due punishment.
On a final note, John gives several mentions to a “bottomless pit” or an “abyss” and in Revelation 20:1-3 he records that Satan will be bound there and is unable to tempt anyone for 1000 years. This is interesting because as I shared in a previous post, it very well may be that we will be in Heaven during the 1000 years and Satan and his evil angels will be bound by chains restraining them because of the circumstances of not having anyone to tempt.