Helm capabilities

In hostile environments, a Tempestus regiment will don all-enclosing omnishield helms, their respmasks proof against everything from industrial pollution to fully ignited atmospheres. When sealed, they allow Tempestus Scions to operate even in airless vacuums for limited periods of time. The multi-spectral occulum that attaches via suction to the wearer's eye sockets allow him to see in low light and occluded conditions with relative ease.

Codex: Militarum Tempestus pg. 8