The suit uses a combination of triple-layer rubberized mesh, reflective shielding, and low-intensity force-field path warps, in order to protect its wearer from not only vacuum but other environmental hazards such as radiation and chemical spills. Competitors such as the "HaziShield Group" and "Wykodyne" have claimed that keeping force-field generators so close to the skin for long periods of time can be carcinogenic, but most wearers are more concerned about short-term hazards and prefer the added protection.
The hazard suit has no minimum skill requirements. This armor provides significant protection against radiation and toxic hazards. This is most useful when navigating highly radiated areas, such as the coolant tunnels on the Engineering Deck. It can be of some use when dealing with foes that have a toxic attack, but you're probably better off with combat armor in that case.
After you're past Engineering, this armor becomes much less useful. One possible reason to keep it around is to be able to more safely approach Grub Eggs (which often spew toxin). With a hazard suit, you probably won't be poisoned by the toxin, and can safely harvest any organs the Egg contains.