HELIUM VS AIR DATA RECOVERY
We all know that helium is lighter than air — that’s why helium-filled balloons float. Inside of an air-filled hard drive there are rapidly spinning disk platters that rotate at a given speed, 7200 rpm for example. The air inside adds an appreciable amount of drag on the platters that in turn requires an appreciable amount of additional energy to spin the platters. Replacing the air inside of a hard drive with helium reduces the amount of drag, thereby reducing the amount of energy needed to spin the platters, typically by 20%.
We also know that after a few days, a helium-filled balloon sinks to the ground. This was one of the key challenges in using helium inside of a hard drive: helium escapes from most containers, even if they are well sealed. It took years for hard drive manufacturers to create containers that could contain helium while still functioning as a hard drive. This container innovation allows helium-filled drives to function at spec over the course of their lifetime.
In November 2013, the first commercially available helium-filled hard drive was introduced by HGST, a Western Digital subsidiary. The 6 TB drive was not only unique in being helium-filled, it was for the moment, the highest capacity hard drive available. Fast forward a little over 4 years later and 12 TB helium-filled drives are readily available, 14 TB drives can be found, and 16 TB helium-filled drives are arriving soon.
Interesting features
Helium drives have a SMART attribute for its helium level. At least my shucked 8TB Elements have it.
Which Drives are Helium?
No <8TB drives use helium, regardless of manufacturer
Not all 8+ TB WDs use helium anymore - there are some air drives out there since they've managed to develop higher density PMR platters.
Unfortunately WD uses the same model number for Helium and non-Helium drives, so the only way to tell is to look at the drive. e.g. the WD80EFAX is an 8TB WD Red, but comes in both Helium and Non-Helium variants. The non-helium variant looks like this, note the breather hole and lack of a smooth metal top or welded edges.
AFAIK all 8TB+ Seagates that aren't SMR (so Barracuda Pro, IronWolf etc.) are all helium.