VACUUM EXPOSURE

In addition to the abilities listed above, Spartan-IVs have the ability to spacewalk. In a survival situation arising from a ship hull breach or emergency evacuation, you can survive for up to five minutes without any equipment, and with minimal mental and physical repercussions. Surviving vacuum exposure can be harrowing for the average human, but your Spartan augmentations make it merely uncomfortable.

Spartan Field Manual Pg 39