Barrapunto

Efectivamente, el pequeño tamaño de las moléculas de helio hace que se usen para la medida de hermeticidad en encapsulados metálicos (como el de un disco duro).

La web de Hitachi está llena de rollo publicitario, pero se pueden encontrar párrafos interesantes como

The benefits of helium are well known. For over a decade, the HDD industry has looked for solutions to leverage helium. However, no one has been able to manage leakage, nor establish a development process that can cost effectively manufacture millions of these drives. Now, after six years of design and rigorous testing, HGST has successfully patented the first helium development process: HelioSeal technology.

In 2013, we raised the standard for storage efficiency, reliability and value by shipping the first helium HDD, the Ultrastar® He6, using our patented production process.

Reliability has always been our hallmark at HGST. Prior to shipping helium-filled drives, we performed long-term reliability testing, with 5,000 drives each running more than 1,000 hours (over 5 million combined hours), showing no seal degradation on any of the drives.

HGST helium drives undergo accelerated stress testing, including high-temperature soaking, thermal cycling, pressure cycling, humidity cycling and shock testing. Every drive is tested for seal integrity during the manufacturing process prior to shipping. Additionally, our helium drives utilize internal environmental telemetry to monitor seal integrity and report any potential issues.

Our HelioSeal platform has proven so successful that we announced our final air-filled product in 2014, placing a target on helium ubiquity by 2017.

Hablan por ahí de que es helio a baja presión, con lo cual es de esperar que tenga menos fugas. Sospecho que tienen bastante estudiado cuál es la velocidad de fugas de su tecnología de sellado, y que coincidirá con el periodo de garantía del disco duro empresarial: cuando se rompa, no sabrás si ha cascado la electrónica o el sellado.

Ahora que lo comentas, si el helio está a una presión más baja que la atmosférica tenderá a entrar aire, no a salir helio.
Creo recordar una idea similar, en el zeppelin Hindenburg la sala de fumadores la tenían al revés, a más alta presión, para que no entrase hidrógeno y causase una explosión.