[Mollari]

Quick question

I've never ruled it that clothing obscures the astral aura of living beings or duel natured. Clothing breathes, has gaps etc.

But a chemically sealed full body armor, and working on an air tank...

Inanimate objects in the astral are completely opaque. So whilst you'll still look like a humanoid walking statue in the astral, do you hide your aura?

[Stainless Steel Devil Rat]

No.

The lore establishes that your aura extends out a bit from the surface of your body and specifically cites extending beyond all-encompassing full body armor.

[Kiirnodel]

I've always thought of it like this: Until the armor becomes more akin to a Vehicle than clothing, then the subject's aura encompass and include the armor. Essentially, armor/clothing is a part of you. You don't think of yourself as walking around and you just happen to be pushing around this shirt and pants that happen to be draped around your body. So until your armor is functioning on the level of "This robot is moving around and I'm just coming along for the ride," your aura will include whatever armor you are wearing, no matter the level of seal and independence from the environment.

[Jack_Spade]

That said, you might have better luck hiding in a large cardboard box - side effects may include for guards to call out "!" 

[Michael Chandra]

Iirc, this is the reason only Cyborgs can ignore Mental spells: There's no aura to target anymore by the point you are a brain in a jar in a container. Anything less, you're a valid astral target still.